file_contexts (specified by SELINUX_FC) is needed both when building
and (re)packaging. We used to use the copy in out/ when building, and
looked for the copy in BOOT/RAMDISK/ when packaging from target_files
zip. With system_root_image enabled, the file_contexts needed for
building and packaging might be different from the one on device. So
we explicitly pack the file as META/file_contexts in target_files zip.
Also refactor out the overriding of selinux_fc property into
common.LoadInfoDict().
Change-Id: I94f9ea6671b3792c12c1c21573840743d63da39a
(cherry picked from commit aa7318c384)
2c15d9eefe