test/kvargs: fix invalid cases check
test/kvargs: fix invalid cases check

The return was not properly placed, and only the first test case
was validated.

Fixes: e495f5435524 ("kvargs: add test case in app/test")
Cc: stable@dpdk.org

Signed-off-by: Olivier Matz <dfcc1510895413197abb4336e39bb0a3906cba71@6wind.com>
Reviewed-by: David Marchand <f28529695cfa9e3e1eb84e7072aa626af4abb18e@redhat.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk