Filter ifaces for uid operations value before combine

Currently, the stats returned by getNetworkStatsUidDetail()
does not filter iface for mUidOperations, it will cause this
API returns the stats that might contain data with unexpected
iface. Thus filter iface for mUidOperations before combining
it into the return stats.

Bug: 235444141
Test: FrameworksNetTests
Change-Id: I81aaacb5682d69022e521a793516373037510742