init-storage: Copy file contexts from rootfs

Apparently, BusyBox's `cp` does NOT copy SELinux contexts when the `-a`
argument is specified.  This differs from GNU coreutils's `cp`, and
explains why the files copied from the rootfs image to the persistent
storage volume were not being labelled correctly.  The `-c` argument is
required.

Now that files are labelled correctly when they are copied, the step to
run `restorecon` is no longer necessary.

overlay/usr/libexec/init-storage

@@ -16,7 +16,7 @@ copy_var() {
 
     echo 'Copying /var contents to data volume'
     mount -o subvol=var "${dev}" "${tmpdir}" || exit
-    cp -auv /var/. "${tmpdir}" || exit
+    cp -acuv /var/. "${tmpdir}" || exit
     umount "${tmpdir}"
 }