Create stream for every call of getNextFullRestoreDataChun.

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