XenAPINFS: Copy volume to glance

related to blueprint xenapinfs-glance-integration

This patch enables to upload XenAPINFS backed cinder volumes to glance
by using the nova glance plugin.

Change-Id: Ie41aa6871fec691556b82501ce3bfdf50898471d
Allow disabling of long-lived SSH connections.

Currently, SSHPool connections are kept alive indefinitely.  This can
be good for many cases, but sometimes it is not desirable.  For
example, this causes unit tests which use SSH to not complete because
of the open connections.  This patch allows users to revert back
to paramiko's regular timeout policy.

Change-Id: Ifa96508b38d90610390c9ec3d48a7de75d02f08b
Move create_cloned_volume() to LVMVolumeDriver.

The implementation of create_cloned_volume() that was in driver.py
relied on functions that aren't declared there, such as
_create_volume(), _copy_volume(), and _sizestr().  Moved the function
to LVMVolumeDriver in lvm.py, where those functions exist.

Change-Id: I5ab77a119b3af0a152a3b5e0c2ff6a5ce196ad0f
Fixes: bug #1112485
Merge "XenAPINFS: Copy volume to glance"
Merge "Move create_cloned_volume() to LVMVolumeDriver."
Merge "Allow disabling of long-lived SSH connections."