ANDROID: Incremental fs: Set credentials before reading/writing

Use same selinux scheme as incfs v2
Fix memory leak.

Bug: 174692664
Test: incfs_test passes
Signed-off-by: Paul Lawrence <paullawrence@google.com>
Change-Id: I6058ddad9d43ba01b2eabd7d3c576f2cc9b42292
Git-commit: d3b8915e
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>