Require python-cinderclient >= 1.0.6

Havana Nova should require python-cinderclient 1.0.6, which includes
support for features implemented in Havana and already being used by
Nova.  (APIs for assisted snapshots, and volume migration.)

(Landed in master in commit 831c7e6d.)

Change-Id: Ie2efb90a6e8b985f9bb8f9604eedd84e0d8a8a45
Closes-Bug: #1230925
Merge "Require python-cinderclient >= 1.0.6" into stable/havana