base driver _do_iscsi_discovery relies on volume['host'] which breaks if called in multi-backend env

[John Griffith]

The base driver file has a mechanism to attempt an iscsi target discovery in cases where the provider info is not present, this mechanism won't work in multi-backend mode because the sendtargets command is formed using volume['host'] to determine what ip to querie. In the case of multi-backend this host entry will look something like: "cinder-host@backend-name", the "@backend-name" is of course invalid for the iscsiadm call and will result in a failure.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/58886

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/58886
Committed: http://github.com/openstack/cinder/commit/d869dee85aa9d32d1a397b954f6583d6bfa60c18
Submitter: Jenkins
Branch: master

commit d869dee85aa9d32d1a397b954f6583d6bfa60c18
Author: john-griffith <email address hidden>
Date: Wed Nov 27 16:38:22 2013 -0700

    Parse out '@' in volume['host'] to do discovery

    The backup method of getting iscsi info is to use
    iscsiadm discovery, however currently that method
    just uses volume['host'] which in the case of
    multi-backend will use "host@backend-name".

    This will cause the discovery to fail of course, so
    this change just parses out the '@' symbol if it's present
    and avoids the problem in the first place.

    This also beefs up the error logging and exception catching
    a bit.

    Parsing out the '@' symbol all the time should be safe as
    the accepted valid chars for hostnames are digits, a-z and
    hyphens.

    Change-Id: Ic45a38bf4c56a4aec6847ab0d29e3b41d35bd3d2
    Closes-Bug: #1250673