Only update PCI stats if they are reported from the host

Not all drivers and hosts may report PCI stats. These should only
be updated if they are actually reported. This will save valuable cycles
and not have any unnecessary database access.

Fixes bug: 1228872

Change-Id: I3e0170638f3820422dbdea5dfb9e02b2de2ceacd
Merge "Only update PCI stats if they are reported from the host"