Updated the getBuildBySHA1 to use the git plugins MergerRecord to determine if the build is a merge. as in some cases the marked and the revision of the build Build had the same SHA1 key even when it was a merge.

Stability update of getBuildByBranch : Check if the BuildDate action is present and that the git revision is preset before comparing. In case the build failed in checkout data might no be available. Furthermore filter out any merge build when looking for a specific branch