Fix for Cumulus_uat build script

The build target used by Cumulus_uat was not running destroyStaleMetadata before the deployment.  This caused issues in some cases where Cumulus_feature_managed_flow was run before Cumulus_uat and left stale metadata in the packaging org causing the Cumulus_uat deploy with test to fail.

The fix is to run destroyStaleMetadata in a try/catch block before the deployment.  If it fails, the deployment will still proceed but the second run of destroyStaleMetadata would also fail causing the build to be marked as failed.