qemu.test.cfg.pmemsave:change it to correct command

qemu/tests/cfg/qmp_command.cfg

@@ -58,7 +58,7 @@
             cmd_return_value = memsave
         - qmp_pmemsave:
             event_cmd_type = host_cmd
-            qmp_cmd = "memsave val=0, size=4096, filename=/var/tmp/pmemsave"
+            qmp_cmd = "pmemsave val=0, size=4096, filename=/var/tmp/pmemsave"
             pre_cmd = "rm -rf /var/tmp/pmemsave"
             post_cmd = "ls /var/tmp/pmemsave; true"
             cmd_result_check = post_contain