Replace hidden NMS API for setting MTU

Replace the hidden NMS setMtu API with calling INetd directly
for incoming ConnectivityService mainline.

Bug: 170598012
Test: atest FrameworksNetTests
Test: manually connect and disconnect network
Change-Id: I6a51d8033b3354824d4cfb953c2bbe3055d00102
1 file changed
tree: fd1f3a5da279a72d9bfaf7d39d4badb5f2450940
  1. core/
  2. services/
  3. tests/