Redis hscan command returns keys and values interleaved.

Our emulated `hscan` only returned keys.  When running on redis > 2.6,
we'd use the real `hscan` and get values interspersed with our keys.
Fix the emulation to behave the same as the real hscan, and fix the
users to expect interleaved keys and values.

Change-Id: Ie796ba8ff3fde8926aa719adc019efbc6c52f9a4
Add script to allow host decommissioning.

Change-Id: I099004f1a98d2fa2ff4e5db1806205f35b195f77