Activate pep8 check that _ is imported

Removed the specification in tox.ini that _ is a builtin so that
it will no longer assume that _ does not need to be imported.

The correct import is:

    from cinder.i18n import _

Activating this check did not flag any violations in cinder.

Change-Id: Ifc789514d2462c059eb9f003fac288e751331ded
Retry remove iscsi target

There is a race in the gate when removing an iscsi
target in the remove export flow where the target
is still active. It's about a 75% failure rate so
simply adding a configurable retry on the delete
call should clean that up.

Change-Id: I8531652e8b80f1c65c9942e109dea01fda5674e0
Closes-Bug: #1363258
Updated from global requirements

Change-Id: Ib06608cdb8ce099ddc5f5f92aa33e6ba3c68e079
Merge "Retry remove iscsi target"
Merge "Activate pep8 check that _ is imported"
Imported Translations from Transifex

For more information about this automatic import see:
https://wiki.openstack.org/wiki/Translations/Infrastructure

Change-Id: I3c97602b295590fb90cba334e6d390e1e52f9be5
Merge "Updated from global requirements"
Merge "Imported Translations from Transifex"