Fix ProcessStatsST column name issue and add test case to cover check (#281)

What I did
Fix ProcessStatsST column issue

Why I did it
#176, when did optimization of the state_db update into batch as dict, not realized "%" is missed, which is a regression issue.
![image](https://github.com/user-attachments/assets/b544ce77-9670-479b-822f-5b7ca74192ba)

How I verified it
Correct typo and added corresponding unit test to cover column name check.

Author: mssonicbld

scripts/procdockerstatsd

@@ -193,9 +193,9 @@ class ProcDockerStats(daemon_base.DaemonBase):
                 ppid = row.get('PPID')
                 update_value['PPID'] = str(ppid)
                 cpu = row.get('%CPU')
-                update_value['CPU'] = str(cpu)
+                update_value['%CPU'] = str(cpu)
                 mem = round(row.get('%MEM'), 1)
-                update_value['MEM'] = str(mem)
+                update_value['%MEM'] = str(mem)
                 stime = row.get('STIME')
                 update_value['STIME'] = str(stime)
                 tty = row.get('TT')

tests/procdockerstatsd_test.py

@@ -36,6 +36,7 @@ def __init__(self, uids, pid, ppid, memory_percent, cpu_percent, create_time, cm
     def uids(self):
         return self._uids
 
+    @property
     def pid(self):
         return self._pid
 
@@ -131,6 +132,11 @@ def test_update_processstats_command(self):
             mock_process_iter.assert_called_once()
         assert(len(pdstatsd.all_process_obj)== 3)
 
+        expected_fields = {'UID', 'PPID', '%CPU', '%MEM', 'STIME', 'TT', 'TIME', 'CMD'}
+        for field in expected_fields:
+            value = pdstatsd.state_db.get('STATE_DB', 'PROCESS_STATS|1234', field)
+            assert value is not None, f"Missing expected field: {field}"
+
     @patch('procdockerstatsd.getstatusoutput_noshell_pipe', return_value=([0, 0], ''))
     def test_update_fipsstats_command(self, mock_cmd):
         pdstatsd = procdockerstatsd.ProcDockerStats(procdockerstatsd.SYSLOG_IDENTIFIER)