Restart nova-compute after modify the config file

The Install the Compute agent for the Telemetry service section of
install-guide doesn't restart the nova-compute service after modify
/etc/nova/nova.conf file, so the configured option will not take
effect timely.

Change-Id: I8b4a14333c0d8d6e0a2633e7c3cf0997d2e46009
Closes-Bug: #1269198
Merge "Restart nova-compute after modify the config file"