Check for circular module loading earlier to avoid deadlock
Check for circular module loading earlier to avoid deadlock

Since precomp processes now take care of their own locking we have to
take that into account and check for circular loading before trying to
lock a destination that's potentially already locked by a parent process.

MasterDuke17/rakudo,salortiz/rakudo,MasterDuke17/rakudo,tony-o/rakudo,rakudo/rakudo,salortiz/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,rakudo/rakudo,rakudo/rakudo,rakudo/rakudo,tony-o/rakudo,tbrowder/rakudo,tbrowder/rakudo,salortiz/rakudo,rakudo/rakudo,tony-o/rakudo,labster/rakudo,rakudo/rakudo,labster/rakudo,labster/rakudo,salortiz/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,salortiz/rakudo,tony-o/rakudo,tony-o/rakudo,labster/rakudo,tbrowder/rakudo,tony-o/rakudo,labster/rakudo,MasterDuke17/rakudo,labster/rakudo,salortiz/rakudo,tbrowder/rakudo