Removes "RPC not enabled" error message when no backend is needed

When no service needing a RPC backend is activated, no error message
should appear if a RPC backend is not installed. A simple check is
done on the services installation files to see which services need to
initialize a RPC backend at some point; if none of these services
are in ENABLED_SERVICES then the error message is skipped.

Change-Id: I4e47e0c675c74775b4ea53a00848ac1d777f0125
Fixes: bug #1167338
Merge "Removes "RPC not enabled" error message when no backend is needed"