IHS-127 Fix branch creation with sync client (#527)

Author: gmazoyer

changelog/374.fixed.md

@@ -0,0 +1 @@
+Fix branch creation with the sync client while setting `wait_until_completion=False`

infrahub_sdk/branch.py

@@ -292,13 +292,14 @@ def create(
             },
         }
 
-        query = Mutation(mutation="BranchCreate", input_data=input_data, query=MUTATION_QUERY_DATA)
+        mutation_query = MUTATION_QUERY_TASK if background_execution else MUTATION_QUERY_DATA
+        query = Mutation(mutation="BranchCreate", input_data=input_data, query=mutation_query)
         response = self.client.execute_graphql(query=query.render(), tracker="mutation-branch-create")
 
         # Make sure server version is recent enough to support background execution, as previously
         # using background_execution=True had no effect.
         if background_execution and "task" in response["BranchCreate"]:
-            return BranchData(**response["BranchCreate"]["task"]["id"])
+            return response["BranchCreate"]["task"]["id"]
         return BranchData(**response["BranchCreate"]["object"])
 
     def delete(self, branch_name: str) -> bool: