[openFATE 305899] Build Service Package Locking

Feature changed by: Andreas Jaeger (a_jaeger) Feature #305899, revision 4 Title: Build Service Package Locking - Buildservice: Unconfirmed + Buildservice: Evaluation Priority Requester: Important Requested by: Will Stephenson (wstephenson) Description: * Lock a package * osc co -l checks out and locks * Anyone can unlock a package (to prevent deadlock) but it has to be explicit * https://build.opensuse.org/project/monitor to show locks and lock owners -- openSUSE Feature: https://features.opensuse.org/305899