NetworkWatchListShellCommand: Close the input file

We were leaking a PFD. Make sure we don't.

Fix: 172655953
Test: atest CtsNetTestCases:android.net.cts.NetworkWatchlistTest#testGetWatchlistConfigHash
Test: Run locally, verify no strict mode error seen.
Change-Id: I05590779f950e8400e8da7477049f8fe3779f0a0
1 file changed