Remove Preconditions usage in TestNetworkSpecifier

Preconditions is a hidden API utility. It can be easily replace by
inline checks.

Bug: 177046265
Test: m
Change-Id: I3f722075fb9c74e12e40348ba4faad2f0fa67178
1 file changed
tree: 9c4ec222c58678fb7592e9b34c1db13d0c7deedb
  1. framework/
  2. service/
  3. OWNERS