conf.c/conf.h: have replaced bool hostid_is_mapped() with int mapped_hostid()
   which returns the mapped uid for the caller's uid on the host, or -1 if
   none

create_run_template: pass caller's uid into template.

lxc-ubuntu-cloud:
	1. accept --mapped-uid argument
	2. don't write to devices cgroup - not allowed.
	3. if running in userns, use $HOME/.cache
	4. chown cached files to the uid to which our caller was
	   mapped
	5. ignore /dev when extracting rootfs in a userns

Changelog: nov 5: remove debugging INFO line.
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>