[hostcfgd]: wait till system initialization is done before starting hostcfgd (#6232)

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

- How I did it
use the command "systemctl is-system-running --wait"  to wait till system has finished booting up before updating the feature states

src/sonic-host-services/scripts/hostcfgd

@@ -300,6 +300,7 @@ class HostConfigDaemon:
         self.kdumpCfg = KdumpCfg(self.config_db)
         self.kdumpCfg.load(self.config_db.get_table('KDUMP'))
 
+
     def load(self):
         aaa = self.config_db.get_table('AAA')
         tacacs_global = self.config_db.get_table('TACPLUS')
@@ -447,6 +448,13 @@ class HostConfigDaemon:
         syslog.syslog(syslog.LOG_INFO, 'Kdump handler...')
         self.kdumpCfg.kdump_update(key, data, False)
 
+    def wait_till_system_init_done(self):
+
+        # No need to print the output in the log file so using the "--quiet"
+        # flag
+        systemctl_cmd = "sudo systemctl is-system-running --wait --quiet"
+        subprocess.call(systemctl_cmd, shell=True)
+
     def start(self):
 
         self.config_db.subscribe('AAA', lambda table, key, data: self.aaa_handler(key, data))
@@ -456,6 +464,12 @@ class HostConfigDaemon:
         self.config_db.subscribe('FEATURE', lambda table, key, data: self.feature_state_handler(key, data))
         self.config_db.subscribe('KDUMP', lambda table, key, data: self.kdump_handler(key, data))
 
+        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()