Run restorecon after init creates a symlink or writes to a file.

Init currently sets the SELinux context on a mkdir but not on
other operations.  This patch modifies it to do so when creating
symlinks, writing to a file, or copying a file.

Test: Built, flashed, and booted.  Added fake init entries and
verified that they received the proper SELinux context.

Change-Id: I836b570fef81d74f3b6c8e7ce0274e94ca7b12d3