Install of a Barbican RPM fails due to missing keystonemiddleware

keystonemiddleware (a dependency added recently) is not yet in RDO but
is a dependency for Barbican, and therefore needs to be FPM-ed via the
rpmbuild/package_dependencies.sh script.

Closes-Bug: #1356574
Change-Id: Iab1879d5529b45ddcfdb28224cba55fdd06d0205