core: Add MaxHostNetworkQosShares configuration value

This will be used to determine the maximum number of allowed shares
given to a specific network - this will be used to set the
granularity/resolution of traffic prioritization by network.

Change-Id: Idfd8df78fd8a06b5e73d1a66f12897d423cdcfe0
Signed-off-by: Lior Vernia <lvernia@redhat.com>