Add more tests in NetworkCapabilitiesTest.java

Test deduceRestrictedCapability(), getAdministratorUids(),
setAdministratorUids(), getNetworkSpecifier(), getOwnerUid(),
setLinkDownstreamBandwidthKbps(), setLinkUpstreamBandwidthKbps()
and setSignalStrength().

Bug: 139268426
Bug: 135998869
Bug: 138306002
Test: atest CtsNetTestCasesLatestSdk:android.net.NetworkCapabilitiesTest
Change-Id: I90c7a8c47710ea4ad8e8d2682c10440fd7f82270