[jail] removal by jid doesn't trigger pre/post stop scripts

This commit fixes bug: command "jail -r" didn't trigger pre/post stop
commands (and others) defined in config file if jid is specified insted of
name. Also it adds basic tests for usr.sbin/jail to avoid regression.

Reviewed by: jamie, kevans, ray
MFC after: 5 days
Differential Revision: https://reviews.freebsd.org/D21328