python-common/smb: work around socket path length limits for grpc lib

The grpc library (at least the version on centos/rocky 10) has a limit
of 107 characters. Even a fairly short host name is going to be close
to this limit due to the UUID and service name in the path.

Because the tool doesn't do much else and it is safe, the workaround is
to chdir to into the parent dir of the socket and only pass the relative
path name of socket.

Fixes: https://tracker.ceph.com/issues/78857
Signed-off-by: John Mulligan <jmulligan@redhat.com>