Adjust CINDER_SECURE_DELETE flag to cinder changes

Cater for the pending more general cinder support
for configurable volume wiping method at:
https://review.openstack.org/#/c/12521

This change is done here first so as to not
trigger a CI lockup when the referenced patch above lands.
When that's in place, we can remove the older
secure_delete config adjustment in a subsequent patch.

Change-Id: I73fe2e0d1cf2815ab6025121584951cb5ff56fa3
Properly wait until volumes are gone in volumes.sh

A logic error in volume exercise's wait for volume deletion
causes the test to do the opopsite, and continue on even tho
the volume is in in the 'deleting' state.  If using a volume
backend that can quickly delete volumes (ceph), and the volume
is gone before entering the wait, the loop will spin, timeout
and fail the test.

Change-Id: I8e3d2aaa04e6a165e0dee32bedac97d35e13d5eb
Use apt git package instead of git-core.

The git-core package is deprecated in favor of the git package. Use the
git package instead.

Change-Id: Ib136e34c7a0d4f87b02e32996420b3f507ca0bf4
Merge "Properly wait until volumes are gone in volumes.sh"
Merge "Use apt git package instead of git-core."
Merge "Adjust CINDER_SECURE_DELETE flag to cinder changes"
fix msec format string

in the else case, which was triggered for devstack gate
the msec format string was incorrect, thus largely scrambling
the usefulness of logs. Fix this to make devstack readable.

Change-Id: I59d0e73932daf27dc1d718dfcf217fe2edf4d491