Move OpenStack update timeout to the settings.py

Make update timeout setting configurable via exporting
environment variable, so it could be tuned for different
deployment scenarios. Also increase timeout value to 1 hour
by default.

Change-Id: I110d9bf1b6c8dd68d38ffc76c0185c55eee87298
Merge "Move OpenStack update timeout to the settings.py" into stable/5.1