xenstore-chmod: handle arbitrary number of perms rather than MAX_PERMS constant

xenstore-chmod: handle arbitrary number of perms rather than MAX_PERMS constant

Constant MAX_PERMS 16 is too small to use in some occasions, e.g. if
there are more than 16 domU(s) on one hypervisor (it's easy to
achieve) and one wants to do xenstore-chmod PATH to all domU(s). So,
remove MAX_PERMS limitation and make it as arbitrary number of perms.

Signed-off-by: Chunyan Liu <cyliu@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>