MFC r197298:

MFC r197298:
Change the default transport protocol for use by the Mount protocol
and the NFS Null RPC done by mount_nfs from UDP to TCP, so that it is
consistent with the kernel, which already uses NFS over TCP by
default. Without this change, doing an NFS mount
against a server that only supports UDP results in an unusable
mount point if a transport protocol option wasn't specified for the
mount.

Approved by:	re (kib)

git-svn-id: svn://svn.freebsd.org/base/stable/8@198150 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f