cephfs admin: add newFSAdmin func for setting up fsadmin test instances
cephfs admin: add newFSAdmin func for setting up fsadmin test instances

Previously, the getFSAdmin function always fetched a cached (if
available) fsadmin instance set up for the default configuration of
ceph. This change makes getFSAdmin based on newFSAdmin a function
that always returns a new instance and allows a custom configuration
to be passed.

Otherwise, newFSAdmin works like getFSAdmin did previously, supporting
debugging via an environment variable.

Signed-off-by: John Mulligan <eda8ad33169deab44f9fe65847f99e368da6c91b@redhat.com>

ceph/go-ceph,ceph/go-ceph,ceph/go-ceph