Pin python-sh version to 1.11.0
Pin python-sh version to 1.11.0

sh 1.12.5 has been released today, and it seems to break DLRN
badly. Pinning to 1.11.0, an old but known-good version, to unblock all
CIs while we investigate.

Change-Id: I6ea3f934e75d8aa70d41ae7d4197a56b6a20b0ea

openstack-packages/DLRN,openstack-packages/delorean,openstack-packages/delorean,openstack-packages/DLRN