[config/main.py] Modify reload() function to load configuration from …

…init_cfg.json implicitly (sonic-net#812)

* [config/main.py] Modify the load() and reload() functions to load config
from config_db.json and init_cfg.json.

Signed-off-by: Yong Zhao <yozhao@microsoft.com>

* [config/main.py] Undo the changes which load the configuration from
init_cfg.json for load() function and define a
constant string for the path of init_cfg.json.

Signed-off-by: Yong Zhao <yozhao@microsoft.com>

* [config/main.py] Correct a typo.

Signed-off-by: Yong Zhao <yozhao@microsoft.com>

* [config/main.py] Added an else statement in line 551 to decide whether
the init_cfg.json exsits or not in reload function.

Signed-off-by: Yong Zhao <yozhao@microsoft.com>

* [config/main.py] Correct a typo error.

Signed-off-by: Yong Zhao <yozhao@microsoft.com>

* [config/main.py] Change the loading order and we should first load
init_cfg.json and then config_db.json.

Signed-off-by: Yong Zhao <yozhao@microsoft.com>

* [config/main.py] Use constant string to represent the path of
init_cfg.json.

Signed-off-by: Yong Zhao <yozhao@microsoft.com>

config/main.py

@@ -27,6 +27,8 @@
 SYSLOG_IDENTIFIER = "config"
 VLAN_SUB_INTERFACE_SEPARATOR = '.'
 
+INIT_CFG_FILE = '/etc/sonic/init_cfg.json'
+
 # ========================== Syslog wrappers ==========================
 
 def log_debug(msg):
@@ -544,7 +546,11 @@ def reload(filename, yes, load_sysinfo):
         command = "{} -H -k {} --write-to-db".format(SONIC_CFGGEN_PATH, cfg_hwsku)
         run_command(command, display_cmd=True)
 
-    command = "{} -j {} --write-to-db".format(SONIC_CFGGEN_PATH, filename)
+    if os.path.isfile(INIT_CFG_FILE):
+        command = "{} -j {} -j {} --write-to-db".format(SONIC_CFGGEN_PATH, INIT_CFG_FILE, filename)
+    else:
+        command = "{} -j {} --write-to-db".format(SONIC_CFGGEN_PATH, filename)
+
     run_command(command, display_cmd=True)
     client.set(config_db.INIT_INDICATOR, 1)