Make sure that only the owner can call stopVpnProfile()

In stopVpnProfile(), it doesn't check if the caller's package
name is the same as the given one, so any app has chance to stop
the VPN profile of other apps.

Bug: 191382886
Test: atest FrameworksNetTests CtsNetTestCases \
      CtsHostsideNetworkTests:HostsideVpnTests
Change-Id: Ib0a6e9ed191ff8c8bd55ce9902d894b6a339ace2
Merged-In: I254ffd1c08ec058d594b4ea55cbae5505f8497cc