qemu-ga: Plug memory leak in guest_fsfreeze_cleanup()

Neglects to free errors allocated by qmp_guest_fsfreeze_thaw().
Spotted by Coverity.

While there, drop the test whether return value is negative (it's
never true), and improve logging.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NLuiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

qga/commands-posix.c

@@ -611,13 +611,14 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
 
 static void guest_fsfreeze_cleanup(void)
 {
-    int64_t ret;
     Error *err = NULL;
 
     if (ga_is_frozen(ga_state) == GUEST_FSFREEZE_STATUS_FROZEN) {
-        ret = qmp_guest_fsfreeze_thaw(&err);
-        if (ret < 0 || err) {
-            slog("failed to clean up frozen filesystems");
+        qmp_guest_fsfreeze_thaw(&err);
+        if (err) {
+            slog("failed to clean up frozen filesystems: %s",
+                 error_get_pretty(err));
+            error_free(err);
         }
     }
 }