Enhanced Feature table to support 'always_enabled' value for state an…

…d auto-restart fields. (#6000)

Added new flag value 'always_enabled' for the state and auto-restart field of feature table

init_cfg.json is updated to initialize state field of database/swss/syncd/teamd feature and auto-restart field of database feature
as always_enabled

Once the state/auto-restart value is initialized as "always_enabled" it is immutable and cannot be change via feature config commands. (config feature..) PR#sonic-net/sonic-utilities#1271

hostcfgd will not take any action if state field value is 'always_enabled'

Since we have always_enabled field for auto-restart updated supervisor-proc-exit-listener
not to have special check for database and always rely on value from Feature table.

scripts/hostcfgd

@@ -252,6 +252,10 @@ class HostConfigDaemon:
 
 
     def update_feature_state(self, feature_name, state, feature_table):
+        if state == "always_enabled":
+            syslog.syslog(syslog.LOG_INFO, "Feature '{}' service is always enabled"
+                          .format(feature_name))
+            return
         has_timer = ast.literal_eval(feature_table[feature_name].get('has_timer', 'False'))
         has_global_scope = ast.literal_eval(feature_table[feature_name].get('has_global_scope', 'True'))
         has_per_asic_scope = ast.literal_eval(feature_table[feature_name].get('has_per_asic_scope', 'False'))