more fixes after doing more manual testing on importing

lib/gitlab/bitbucket_import/project_creator.rb

@@ -24,7 +24,8 @@ module Gitlab
         ).execute
 
         import_data = project.import_data
-        import_data.credentials.merge!("bb_session" => session_data)
+        # merge! with a bang doesn't work here
+        import_data.credentials = import_data.credentials.merge("bb_session" => session_data)
         import_data.save
 
         project

lib/gitlab/fogbugz_import/project_creator.rb

@@ -25,7 +25,8 @@ module Gitlab
         ).execute
 
         import_data = project.import_data
-        import_data.credentials.merge!('fb_session' => fb_session)
+        # merge! with a bang doesn't work here
+        import_data.credentials = import_data.credentials.merge('fb_session' => fb_session)
         import_data.data = { 'repo' => repo.raw_data, 'user_map' => user_map }
         import_data.save