mon: let users specify a crush location on boot, and send it in MMonJoin

mon: let users specify a crush location on boot, and send it in MMonJoin

Go to some effort to look at our location in the monmap and update it the
same way we update names or IP addresses when necessary. Let users
pass in the location on the CLI via "--set-crush-location".

Signed-off-by: Greg Farnum <gfarnum@redhat.com>
(cherry picked from commit 48886aa12a351919d8165d449c2fb72a896fc589)