Clean up use of pipe

Don't duplicate what's already in unique_fd.h
Also, code that tries to handle weird stdout condition won't work
because of cloexec; just don't try that.

My tests:
- Ensure Marlin device boots and vold_prepare_subdirs is called
successfully
- Try adb shell sm set-virtual-disk true, see that eg sgdisk output is
logged.

Bug: 26735063
Bug: 113796163
Test: details in commit
Change-Id: I5698ba0b4c8bd692a740a1bd445e677ad4815d11
1 file changed