Make <host>:<port> parsing uniform treewide.

Make <host>:<port> parsing uniform treewide.

I didn't realize until now that the tree had two different ways of parsing
strings in the form <host>:<port> and <port>:<host>.  There are the
long-standing inet_parse_active() and inet_parse_passive() functions, and
more recently the ipv46_parse() function.  This commit eliminates the
latter and changes the code to use the former.

The two implementations interpreted some input differently.  In particular,
the older functions required IPv6 addresses to be [bracketed], but the
newer ones do not.  For compatibility this patch changes the merged code to
use the more liberal interpretation.

Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Mark Michelson <mmichels@redhat.com>