tests: Make dpp_auth_req_retries* more reliable

tests: Make dpp_auth_req_retries* more reliable

These test cases were failing when run immediately after
dpp_pkex_test_fail. It looks like timing of the TX status and the short
eloop wait were getting reordered in this cases. This ended up with some
of the DPP-TX-STATUS event messages missing. Instead of explicitly
checking for those message, simply count the number of DPP-TX messages
to verify that the correct number of retries are being sent.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>