examples/abort: fail when no controllers are found

Otherwise, the test using this application will succeed, even if no test
is actually executed.

Signed-off-by: Konrad Sztyber <konrad.sztyber@intel.com>
Change-Id: Ib2235795ea51985d418c2be6904a68db15aa593a
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/10772
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>

examples/nvme/abort/abort.c

@@ -1096,6 +1096,7 @@ int main(int argc, char **argv)
 
 	if (g_num_namespaces == 0) {
 		fprintf(stderr, "No valid NVMe controllers found\n");
+		rc = -1;
 		goto cleanup;
 	}