Use bindServiceAsUser to bind PacService and ProxyService

PacService and ProxyService should be running on system user.
Use bindServiceAsUser with UserHandle.SYSTEM to start the
services.

Bug: 192114565
Test: CtsNetTestCases:PacProxyManagerTest on target aosp_cf_x86_auto
Change-Id: I88d1bfa1e482a072674f0b96dda027aa1f92d93f
1 file changed