VOL-1446 : Cleanup of db/model unit tests

- Fixed issues with model components while running tests
- Removed unecessary tests

Change-Id: Ica2007b66f681d03a77144cf2e778aa5a586786a
diff --git a/db/model/branch.go b/db/model/branch.go
index 2ad40b4..40c66ad 100644
--- a/db/model/branch.go
+++ b/db/model/branch.go
@@ -89,7 +89,7 @@
 	b.Lock()
 	defer b.Unlock()
 
-	if revision, ok := b.Revisions[hash]; !ok {
+	if revision, ok := b.Revisions[hash]; ok {
 		return revision
 	}