feat: add null hostkey for server

fix: skip gssapi tests in fips mode

fix: skip gssapi_key_exchange_null test on ubuntu and tumbleweed

fix: return early when rc != 0 to show error

tests: replace int asserts by ssh return code asserts

fix: add fatal error when hostkeys are not found and gssapi kex is not enabled

ci: add comment linking gssapi null kex bug in ubuntu and tumbleweed

fix: don't specify hostkeys in config instead of deleting files

tests: assert kex method was null

refactor: remove redundant include

refactor: better error message

fix: check null before accessing in gssapi.c

fix: allow setting no hostkeys
Signed-off-by: Gauravsingh Sisodia <xaerru@gmail.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

tests/server/torture_gssapi_server_delegation.c

@@ -372,5 +372,11 @@ torture_run_tests(void)
                                 teardown_default_server);
     ssh_finalize();
 
-    return rc;
+    /* pthread_exit() won't return anything so error should be returned prior */
+    if (rc != 0) {
+        return rc;
+    }
+
+    /* Required for freeing memory allocated by GSSAPI */
+    pthread_exit(NULL);
 }