test(hotplug): enable RSS assertion for secret_free and fix VM leak

Now that discard_range() uses fallocate(PUNCH_HOLE) for guest_memfd,
and get_resident_memory() uses guest meminfo for secret_free VMs,
the RSS decrease assertion in check_hotunplug works correctly for
secret_free. Remove the skip.

Signed-off-by: Jack Thomson <jackabt@amazon.com>

Author: JackThomson2

tests/integration_tests/performance/test_hotplug_memory.py

@@ -289,8 +289,10 @@ def check_hotunplug(uvm, requested_size_mib):
     machine_config = uvm.api.machine_config.get().json()
     huge_pages = HugePagesConfig(machine_config["huge_pages"])
     secret_free = machine_config.get("secret_free", False)
-    if not secret_free and (
-        huge_pages == HugePagesConfig.NONE or supports_hugetlbfs_discard()
+    if (
+        secret_free
+        or huge_pages == HugePagesConfig.NONE
+        or supports_hugetlbfs_discard()
     ):
         assert rss_after < rss_before, "RSS didn't decrease"