If someone specifies --with-verbs-usnic, actually do a configury check
to ensure that it will compile (vs. assuming that it will compile if
someone asks for it).
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
(cherry picked from commit 05e5f61fe1c961927eae5bb5c0eb2021ac99afa6)
3e842348d1