net/handshake: Squelch allocation warning during Kunit test

The "handshake_req_alloc excessive privsize" kunit test is intended
to check what happens when the maximum privsize is exceeded. The
WARN_ON_ONCE_GFP at mm/page_alloc.c:4744 can be disabled safely for
this test.

Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Fixes: 88232ec1 ("net/handshake: Add Kunit tests for the handshake consumer API")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://lore.kernel.org/r/168451636052.47152.9600443326570457947.stgit@oracle-102.nfsv4bat.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>