This patch introduces a new 'vzDriver' lockable object and provides
helper functions to allocate/destroy it and we pass it to prlsdkXxx
functions instead of virConnectPtr.
Now we store domain related objects such as domain list, capabitilies
etc. within a single vz_driver vzDriver structure, which is shared by
all driver connections. It is allocated during daemon initialization or
in a lazy manner when a new connection to 'vz' driver is established.
When a connection to vz daemon drops, vzDestroyConnection is called,
which in turn relays disconnect event to all connection to 'vz' driver.
Signed-off-by: NMaxim Nestratov <mnestratov@virtuozzo.com>