Drop the thread mutex.  Set a (TLS) boolean at container start to
indicate that the connection should be kept open;  set it back to false
only when container start is complete.  Every cgm_ method opens the
connection if not already open, and closes it if cgm_keep_connection
is false.
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>