Fix invalid facilities documented in rootwrap.conf

The values user0 and user1 do not map to valid facility values.
local1, etc.  Using user0 results in a  pri value that does not map
back to a facility of the same name in syslog.

RFC5424 suggest values values of local0 through local7.  Setting
syslog_log_facility to one of those values results in a message with a
priority that can be mapped back to the original string value.

This fix adjusts the comment in rootwrap.conf to suggest the local
prefix instead of the user prefix.

Closes-Bug #1280879

Change-Id: Ibefffb5619641b75b4f8ac8ce8112a34cf03f0ce
Merge "Fix invalid facilities documented in rootwrap.conf"