tests: fix -Wmaybe-uninitialized warnings

Fix the following class of compilation warnings reported by gcc 11:

tst-pam_end.c: In function ‘main’:
tst-pam_end.c:55:12: error: ‘conv’ may be used uninitialized [-Werror=maybe-uninitialized]
   55 |   retval = pam_start (service, user, &conv, &pamh);
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from tst-pam_end.c:41:
../libpam/include/security/pam_appl.h:23:1: note: by argument 3 of type ‘const struct pam_conv *’ to ‘pam_start’ declared here
   23 | pam_start(const char *service_name, const char *user,
      | ^~~~~~~~~
tst-pam_end.c:49:19: note: ‘conv’ declared here
   49 |   struct pam_conv conv;
      |                   ^~~~

* tests/tst-pam_end.c (main): Initialize conv variable.
* tests/tst-pam_fail_delay.c: Likewise.
* tests/tst-pam_get_item.c: Likewise.
* tests/tst-pam_getenvlist.c: Likewise.
* tests/tst-pam_set_data.c: Likewise.
* tests/tst-pam_set_item.c: Likewise.
* tests/tst-pam_start.c: Likewise.
* tests/tst-pam_start_confdir.c: Likewise.

8 files changed, 8 insertions, 8 deletions

diff --git a/tests/tst-pam_end.c b/tests/tst-pam_end.c
index 93c2fc32..d79df7c6 100644
--- a/tests/tst-pam_end.c
+++ b/tests/tst-pam_end.c
@@ -46,7 +46,7 @@ main (void)
 {
   const char *service = "dummy";
   const char *user = "root";
-  struct pam_conv conv;
+  struct pam_conv conv = { NULL, NULL };
   pam_handle_t *pamh;
   int retval;
 
diff --git a/tests/tst-pam_fail_delay.c b/tests/tst-pam_fail_delay.c
index c4323178..d81c5765 100644
--- a/tests/tst-pam_fail_delay.c
+++ b/tests/tst-pam_fail_delay.c
@@ -46,7 +46,7 @@ main (void)
 {
   const char *service = "dummy";
   const char *user = "root";
-  struct pam_conv conv;
+  struct pam_conv conv = { NULL, NULL };
   pam_handle_t *pamh;
   int retval;
 
diff --git a/tests/tst-pam_get_item.c b/tests/tst-pam_get_item.c
index 2b0cc7e2..c6e3d9fa 100644
--- a/tests/tst-pam_get_item.c
+++ b/tests/tst-pam_get_item.c
@@ -66,7 +66,7 @@ main (void)
 {
   const char *service = "dummy";
   const char *user = "root";
-  struct pam_conv conv;
+  struct pam_conv conv = { NULL, NULL };
   pam_handle_t *pamh;
   int retval;
   unsigned int i;
diff --git a/tests/tst-pam_getenvlist.c b/tests/tst-pam_getenvlist.c
index d24a9bf9..a1184f1a 100644
--- a/tests/tst-pam_getenvlist.c
+++ b/tests/tst-pam_getenvlist.c
@@ -48,7 +48,7 @@ main (void)
 {
   const char *service = "dummy";
   const char *user = "root";
-  struct pam_conv conv;
+  struct pam_conv conv = { NULL, NULL };
   pam_handle_t *pamh;
   int retval;
   char **ptr;
diff --git a/tests/tst-pam_set_data.c b/tests/tst-pam_set_data.c
index 9acab6a6..d1eaa3ea 100644
--- a/tests/tst-pam_set_data.c
+++ b/tests/tst-pam_set_data.c
@@ -275,7 +275,7 @@ main (void)
 {
   const char *service = "dummy";
   const char *user = "root";
-  struct pam_conv conv;
+  struct pam_conv conv = { NULL, NULL };
   pam_handle_t *pamh;
   void *dataptr;
   int retval;
diff --git a/tests/tst-pam_set_item.c b/tests/tst-pam_set_item.c
index bd17e11a..3457b49c 100644
--- a/tests/tst-pam_set_item.c
+++ b/tests/tst-pam_set_item.c
@@ -67,7 +67,7 @@ main (void)
 {
   const char *service = "dummy";
   const char *user = "root";
-  struct pam_conv conv;
+  struct pam_conv conv = { NULL, NULL };
   pam_handle_t *pamh;
   int retval;
   unsigned int i;
diff --git a/tests/tst-pam_start.c b/tests/tst-pam_start.c
index ce013633..8fa18f74 100644
--- a/tests/tst-pam_start.c
+++ b/tests/tst-pam_start.c
@@ -46,7 +46,7 @@ main (void)
 {
   const char *service = "dummy";
   const char *user = "root";
-  struct pam_conv conv;
+  struct pam_conv conv = { NULL, NULL };
   pam_handle_t *pamh;
   int retval;
 
diff --git a/tests/tst-pam_start_confdir.c b/tests/tst-pam_start_confdir.c
index e40b6e70..f731b2a5 100644
--- a/tests/tst-pam_start_confdir.c
+++ b/tests/tst-pam_start_confdir.c
@@ -50,7 +50,7 @@ main (void)
   const char *user = "root";
   const char *confdir;
   const char *xconfdir = "/nonexistent-confdir";
-  struct pam_conv conv;
+  struct pam_conv conv = { NULL, NULL };
   pam_handle_t *pamh;
   int retval;