Before we where keeping the same stream for different calls, and the
fileDescriptor was different so we could end up writting to an invalid
file descriptor.
Test: Run adb backup and restore of wallpaper package that was failing.
Test: cts-tradefed run commandAndExit cts -m CtsBackupHostTestCases
BUG: 117139223
Change-Id: I0d696a0e114f35427514730b0067b169f1bed08a