Use full ref when creating MR pipeline in specs

Continuation of 426488b7

spec/services/ci/create_pipeline_service_spec.rb

@@ -923,7 +923,7 @@ describe Ci::CreatePipelineService do
             let(:merge_request) do
               create(:merge_request,
                 source_project: project,
-                source_branch: ref_name,
+                source_branch: Gitlab::Git.ref_name(ref_name),
                 target_project: project,
                 target_branch: 'master')
             end
@@ -954,7 +954,7 @@ describe Ci::CreatePipelineService do
             let(:merge_request) do
               create(:merge_request,
                 source_project: project,
-                source_branch: ref_name,
+                source_branch: Gitlab::Git.ref_name(ref_name),
                 target_project: project,
                 target_branch: 'master')
             end
@@ -983,7 +983,7 @@ describe Ci::CreatePipelineService do
             let(:merge_request) do
               create(:merge_request,
                 source_project: project,
-                source_branch: ref_name,
+                source_branch: Gitlab::Git.ref_name(ref_name),
                 target_project: project,
                 target_branch: 'master')
             end