Avoid fd to be closed by ParcelFileDescriptor's finalizer

testBlockIncomingPacketsis flaky since ParcelFileDescriptor's
finalizer closes fd and makes fd invalid.
This CL fixes this issue by keeping the reference to
ParcelFileDescriptor.

Bug: 394503660
Test: testBlockIncomingPackets
Change-Id: I1c1645d95b9d9ae1bd5af4ada500f50f350b6b0b
1 file changed