Remove exclusivity restriction of multiple preferences

- Each network preference has been assigned a priority value so
  that netd can know which uid range rule has higher priority. So
  remove the restriction that all network preferences are
  exclusive.
- Add priority check when getting request for uid.

Bug: 171872461
Test: atest FrameworksNetTests
Ignore-AOSP-First: Needs cherry-picks
Change-Id: I6912db753c8b4a194aa7af92b01ca6dcfec10d8b
2 files changed