getport: Remove AI_ADDRCONFIG from nfs_gp_loopback_address()

getport: Remove AI_ADDRCONFIG from	nfs_gp_loopback_address()

AI_ADDRCONFIG was used ostensibly to figure out if the local system
had IPv6 available when generating a loopback address.

A legacy version of nfs_gp_loopback_address() was created to handle
ANYADDR address generation for old versions of glibc where
AI_ADDRCONFIG doesn't exist.  This means we have to be careful to
test both the normal and legacy versions when committing changes in
this area.

But it turns out that even contemporary versions of glibc ignore
AI_ADDRCONFIG when the hostname string is NULL.  getaddrinfo(3)
always returns an AF_INET and an AF_INET6 loopback address in this
case, no matter how the system is configured.

Change nfs_gp_loopback_address() to have one version that simply looks
up "localhost" instead of doing anything fancy.  If "localhost" is an
IPv6 address, we'll use that.  Otherwise, it should nearly always be
an AF_INET loopback address.

This eliminates the need for AI_ADDRCONFIG, and removes the duplicate
version of nfs_gp_loopback_address().  Note that callers never used
the port number in the returned socket address, so get rid of the
"sunrpc" service string too.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Steve Dickson <steved@redhat.com>