ceph-conf: fix client's admin socket parsing

ceph-conf: fix client's admin socket parsing

For the 'admin socket' in ceph.conf, if the "$pid" is specified, it
will be expanded with the current process's PID.

For the ceph-conf command, if we specify the "--name" with a value
that have contained a socket daemon's PID, likes:

$ ceph-conf --name client.admin.133423 --show-config-value admin_socket

It will return a sockpath like:

/tmp/user/1000/ceph-asok.EZQumU/client.admin.133423.324523.asok

But the following is expected:

/tmp/user/1000/ceph-asok.EZQumU/client.admin.133423.asok

Stick "$name.$id" for mon/osd/mds/mgr daemons and for other try to
tripe the "$pid" from the name option's value and set a "PID" env.

Fixes: https://tracker.ceph.com/issues/47977
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Kefu Chai <kchai@redhat.com>