Perftest: Fix BW degradation with --output flag due to CPU starvation

When using '--output=bandwidth', skipping print headers causes the test
to enter the polling loop immediately, starving the CPU core handling NIC
interrupts.
This leads to significant performance drops (e.g., ~50%) on local socket
cores.

Add a usleep(1) to yield the CPU before starting measurement, allowing
interrupts to be processed correctly.

Signed-off-by: Shmuel Shaul <sshaul@nvidia.com>

Author: sshaulnv

src/perftest_parameters.c

@@ -4039,8 +4039,10 @@ void ctx_print_test_info(struct perftest_parameters *user_param)
 {
 	int temp = 0;
 
-	if (user_param->output != FULL_VERBOSITY)
+	if (user_param->output != FULL_VERBOSITY){
+		usleep(1); /* Yield CPU to prevent interrupt starvation on the local socket before the test starts */
 		return;
+	}
 
 	printf(RESULT_LINE);
 	printf("                    ");