Use new test utilities from frameworks/libs/net

Use runAsShell from the new TestPermissionUtils, and rename popPacket to
poll.

This rolls forward the previous change as-is. See change
I34bad7ec79ef0fd03e5e40b643f0d85d686c53ec for details on why the
previous change was reverted.

Bug: 168868607
Test: atest CtsNetTestCasesLatestSdk
Change-Id: I7b5176e84ffe08cc5ea1251f66cdcb9b7066ec0a
3 files changed