The previous change was flawed in terms of how it calculated the
buffer length for the sockaddr_un object. Use SUN_LEN where
appropriate and mute the Coverity complaint by using memset(.., 0, ..)
to zero out the entire structure instead of setting .sun_len to a bogus
value and strlcpy'ing in the contents of argv[1].
SUN_LEN is now being passed to bind(2) as well. For some odd reason
this wasn't flagged as a bug with Coverity.
Reported by: jilles, jmallett
MFC after: 2 days
X-MFC with: r311233
19b32b04f2