Give more meaningful message if a lock is found

[jose1711]

Currently when a backup is attempted while the lock is present vorta displays a warning:

I think it would be nice an extra piece of information could be shown when:

• borgfs is mounted on a local machine (with an option to unmount directly from UI)
• other borg process(es) exist(s) on a local machine (together with UID, start time and command arguments)