test_sorcery_memory_cache_thrash: Handle error from vector append.

Cleanup resources when we fail to append the vector and report test
failure.

Change-Id: I6eb41586fd11dee8c0dfe35e91cb465a4cab7298

tests/test_sorcery_memory_cache_thrash.c

@@ -218,7 +218,11 @@ static struct sorcery_memory_cache_thrash *sorcery_memory_cache_thrash_create(co
 		/* This purposely holds no ref as the main thrash structure does */
 		thread->sorcery = thrash->sorcery;
 
-		AST_VECTOR_APPEND(&thrash->threads, thread);
+		if (AST_VECTOR_APPEND(&thrash->threads, thread)) {
+			ast_free(thread);
+			ao2_ref(thrash, -1);
+			return NULL;
+		}
 	}
 
 	return thrash;