RemoteFS driver should initialize shares variables

[Eric Harney]

RemoteFS driver's code volume mounting code (_ensure_shares_mounted) assumes that self.shares and self._mounted_shares exist, but they are not initialized in __init__. Instead, it is currently required that subclasses initialize these variables.

They should be initialized to None in __init__ so that they always exist. This fixes pylint warnings to this effect, and also makes it less complicated for anyone working on drivers based on this class.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/49413
Committed: http://github.com/openstack/cinder/commit/7e37cd80fe12eabaafba5c5c1c8f35413f193e37
Submitter: Jenkins
Branch: master

commit 7e37cd80fe12eabaafba5c5c1c8f35413f193e37
Author: Eric Harney <email address hidden>
Date: Wed Oct 2 14:11:31 2013 -0400

    Initialize shares variables for RemoteFsDriver(s)

    self.shares and self._mounted_shares are used by various methods
    for RemoteFs-based drivers, but may not be instantiated early enough.

    Initialize them in __init__ to ensure they always exist. (Also fixes
    pylint warnings.)

    Closes-Bug: #1239741
    Change-Id: I0ef884c28b82b7f694cf8a0fb4629c835da11c91