[201911][hostcfgd]:wait updating the feature table till system init is done (#6234)

- Why I did it
The change is done to make sure the system initialization is done before the hostcfgd sets the feature states.

- How I did it
This is port of the PR #6232.
Since the systemctl version in 201911 doesn't support "--wait".
Added a function to check the output of systemctl is-system-running every second, till the command system is done booting up.

For now this change is only applicable to multi asic platforms based on the testing this change will be extended to all platforms in the future PR.

Signed-off-by: Arvindsrinivasan Lakshmi Narasimhan <arlakshm@microsoft.com>

files/image_config/hostcfgd/hostcfgd

@@ -3,6 +3,7 @@
 
 import ast
 import os
+import time
 import sys
 import subprocess
 import syslog
@@ -247,6 +248,20 @@ class HostConfigDaemon:
         lpbk_table = self.config_db.get_table('LOOPBACK_INTERFACE')
         self.iptables.load(lpbk_table)
 
+    def wait_till_system_init_done(self):
+        systemctl_cmd = "sudo systemctl is-system-running"
+        while True:
+            proc = subprocess.Popen(
+                systemctl_cmd,
+                shell=True,
+                stdout=subprocess.PIPE,
+            )
+            output = proc.communicate()[0].rstrip('\n')
+            if output.lower() in ["initializing", "starting"]:
+                time.sleep(1)
+                continue
+
+            return
 
     def update_feature_state(self, feature_name, state, feature_table):
         if state == "always_enabled":
@@ -383,6 +398,13 @@ class HostConfigDaemon:
         self.config_db.subscribe('LOOPBACK_INTERFACE', lambda table, key, data: self.lpbk_handler(key, data))
         self.config_db.subscribe('FEATURE', lambda table, key, data: self.feature_state_handler(key, data))
 
+        if self.is_multi_npu:
+            syslog.syslog(syslog.LOG_INFO,
+                          "Waiting for systemctl to finish initialization")
+            self.wait_till_system_init_done()
+            syslog.syslog(syslog.LOG_INFO,
+                          "systemctl has finished initialization -- proceeding ...")
+
         # Update all feature states once upon starting
         self.update_all_feature_states()