fix(tests/virtio-mem): poll every 5ms in performance tests

Increase granularity of total time measurement from 100ms to 5ms as the
fastest hotplug is around 30ms.

We need to poll the GET API to monitor when plugged_memory_mib is equal
to requested_memory_mib.

Signed-off-by: Riccardo Mancini <mancio@amazon.com>

Author: Manciukic

tests/integration_tests/performance/test_hotplug_memory.py

@@ -410,7 +410,8 @@ def timed_memory_hotplug(uvm, size, metrics, metric_prefix, fc_metric_name):
 
     uvm.flush_metrics()
 
-    api_time, total_time = uvm.hotplug_memory(size)
+    # poll every 5ms to check completion as the fastest hotplug is around 30ms
+    api_time, total_time = uvm.hotplug_memory(size, poll=0.005)
 
     fc_metrics = uvm.flush_metrics()