libceph: add function that reset client's entity addr

This function also re-open connections to OSD/MON, and re-send in-flight
OSD requests after re-opening connections to OSD.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>