[#2254] Added salt to re cache mutex and shared memory name

We incorporate the cache salt into the rule engine's named_mutex and
shared memory object. This prevents (most of the time) an orphaned mutex
from halting server standup. Issue most often seen when a running iRODS
installation is uncleanly killed (leaving the file system object used to
implement boost::named_mutex e.g. in /var/run/shm) and then the iRODS
user account is recreated, yielding a different UID. The new iRODS user
account is then unable to unlock or remove the existing mutex, blocking
the server.