Add support for -R (recurse) to init chown builtin.

This is helpful for setting ownerships on entire directory trees,
such as sysfs and selinuxfs, particularly when the precise set of
files is dynamically generated at runtime.

Change-Id: I81070ea36fd7ffcab4ee8b3ef1bb0028d4b7839c
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>