Currently nfs4mount() sets the retry value to 10000 on both fg and bg

mounts. It should be 2 for fg and 10000 for bg. nfsmount() sets it
properly, but there is a potential corner case. If someone explicitly
sets retry=10000 on a fg mount, then it will be reset to 2.

Fix this by having retry default to -1 for both flavors, and then reset if
needed after the mount options have been parsed.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>