the unix_addr_fs macro should not check for a leading /, instead it
should be checking for the addr not being an abstract socket addr
(leading \0)

BugLink: http://bugs.launchpad.net/bugs/1390223Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>