qemu.balloon_check: reset the memory to origin value

The memory should be reset to the origin value after
evict or enlarge. So that the next iterations tests can
pass when check memory before test
Signed-off-by: NMike Qiu <qiudayu@linux.vnet.ibm.com>

qemu/tests/balloon_check.py

@@ -219,4 +219,14 @@ def run_balloon_check(test, params, env):
             ballooned_mem = 0
         memory_check("after subtest when enlarging memory", ballooned_mem,
                     monitor_boot_mem , guest_boot_mem, ratio)
+
+    # we should reset the memory to the origin value, so that next
+    # iterations can pass when check memory before test
+    error.context("Reset the memory to monitor boot memory", logging.info)
+
+    balloon_memory(monitor_boot_mem)
+    ballooned_mem = vm_assigned_mem - monitor_boot_mem
+    memory_check("after reset memory", ballooned_mem,
+                 monitor_boot_mem, guest_boot_mem, ratio)
+
     session.close()