test/service: fix wait for service core

test/service: fix wait for service core

This commit fixes a sporadic failure of the service_autotest
unit test, as seen in the DPDK CI. The failure occurs as the main test
thread did not wait on the service-thread to return, and allowing it
to read a flag before the service was able to write to it.

The fix changes the wait API call to specific the service-core ID,
and this waits for cores with both ROLE_RTE and ROLE_SERVICE.

The rte_eal_mp_wait_lcore() call does not (and should not) wait
for service cores, so must not be used to wait on service-cores.

Fixes: f038a81e1c56 ("service: add unit tests")
Cc: stable@dpdk.org
Reported-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: David Marchand <david.marchand@redhat.com>