[config reload]: fix the condition for checking if system is starting (sonic-net#1766)

When systemd services finished, the systemd status could running
or degraded. Therefore, compare system status with starting directly.

Here is what is happening on kvm switch. Some services cannot be started.
Then, the system state is in degraded state.

```
admin@ARISTA01T1:~$ systemctl is-system-running
starting
admin@ARISTA01T1:~$ systemctl is-system-running
degraded
```

Signed-off-by: Guohan Lu <[email protected]>

Author: lguohan

config/main.py

@@ -43,7 +43,7 @@
 from . import vxlan
 from . import plugins
 from .config_mgmt import ConfigMgmtDPB
-from . import mclag 
+from . import mclag
 
 # mock masic APIs for unit test
 try:
@@ -727,9 +727,9 @@ def _swss_ready():
     else:
         return False
 
-def _system_running():
+def _is_system_starting():
     out = clicommon.run_command("sudo systemctl is-system-running", return_cmd=True)
-    return out.strip() == "running"
+    return out.strip() == "starting"
 
 def interface_is_in_vlan(vlan_member_table, interface_name):
     """ Check if an interface is in a vlan """
@@ -1233,7 +1233,7 @@ def reload(db, filename, yes, load_sysinfo, no_service_restart, disable_arp_cach
        <filename> : Names of configuration file(s) to load, separated by comma with no spaces in between
     """
     if not force and not no_service_restart:
-        if not _system_running():
+        if _is_system_starting():
             click.echo("System is not up. Retry later or use -f to avoid system checks")
             return
 
@@ -1491,10 +1491,10 @@ def load_port_config(config_db, port_config_path):
     # Validate if the input is an array
     if not isinstance(port_config_input, list):
         raise Exception("Bad format: port_config is not an array")
-    
+
     if len(port_config_input) == 0 or 'PORT' not in port_config_input[0]:
         raise Exception("Bad format: PORT table not exists")
-        
+
     port_config = port_config_input[0]['PORT']
 
     # Ensure all ports are exist