tests: tpm: Use g_test_message rather than fprintf

Display a message during the test using g_test_message rather
than fprintf.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>

tests/tpm-tests.c

@@ -22,7 +22,7 @@ static bool
 tpm_test_swtpm_skip(void)
 {
     if (!tpm_util_swtpm_has_tpm2()) {
-        fprintf(stderr, "swtpm not in PATH or missing --tpm2 support; ");
+        g_test_message("swtpm not in PATH or missing --tpm2 support");
         return true;
     }