Description of problem:
dirty-rate is divided by calc-time when calculate guest dirty-rate

Version-Release number of selected component (if applicable):
host info:
kernel-4.18.0-275.el8.x86_64&qemu-kvm-5.2.0-3.module+el8.4.0+9499+42e58f08.x86_64
guest info:
kernel-4.18.0-275.el8.x86_64

How reproducible:
100%

Steps to Reproduce:
1.Boot a guest on src host, please see qemu command[1];
2.Run stress in guest

1. stressapptest -M 200 -s 100000
   3.Query dirty rate via qmp cmds
   (1)Scenario 1: set calc-time to 3:
   {"execute":"calc-dirty-rate", "arguments": {"calc-time": 3}}
   (2)Scenario 2: set calc-time to 1:
   {"execute":"calc-dirty-rate", "arguments": {"calc-time": 1}}
   after (1) or (2), check dirty rate: {"execute":"query-dirty-rate"}

Actual results:
After step 3, get different dirty rate between Scenario 1 and Scenario 2 on src host:
{"execute":"calc-dirty-rate", "arguments": {"calc-time": 3}}
{"return": {}}

{"execute":"query-dirty-rate"}

{"return": {"status": "measured", "dirty-rate": 61, "start-time": 218710, "calc-time": 3}}
{"execute":"calc-dirty-rate", "arguments": {"calc-time": 3}}
{"return": {}}

{"execute":"query-dirty-rate"}

{"return": {"status": "measured", "dirty-rate": 58, "start-time": 219020, "calc-time": 3}}
{"execute":"calc-dirty-rate", "arguments": {"calc-time": 1}}
{"return": {}}

{"execute":"query-dirty-rate"}

{"return": {"status": "measured", "dirty-rate": 204, "start-time": 219044, "calc-time": 1}}
{"execute":"calc-dirty-rate", "arguments": {"calc-time": 1}}
{"return": {}}

{"execute":"query-dirty-rate"}

{"return": {"status": "measured", "dirty-rate": 196, "start-time": 219068, "calc-time": 1}}
{"execute":"calc-dirty-rate", "arguments": {"calc-time": 3}}
{"return": {}}

{"execute":"query-dirty-rate"}

{"return": {"status": "measured", "dirty-rate": 60, "start-time": 219082, "calc-time": 3}}
{"execute":"calc-dirty-rate", "arguments": {"calc-time": 1}}
{"return": {}}

{"execute":"query-dirty-rate"}

Notes: have checked the stressapptest program, it works well.

Expected results:
The dirty-rate shouldn't be divided by calc-time.

Additional info:
https://bugzilla.redhat.com/show_bug.cgi?id=1833235#c14