Update SonicDBConfig APIs for centralize_database (#1441)

The DB backup during warmboot has started failing recently after the changes made to deprecate the usage of SonicDBConfig methods originally implemented by python in https://github.com/Azure/sonic-py-swsssdk/. The new implementation is based on hiredis C++ library.

How I did it: The centralize_database script still uses the Python APIs instead of C++, update the method names which are now defined in sonic-swss-common.
With the new changes, the warm-boot goes ahead without DB save errors.

scripts/centralize_database

@@ -6,19 +6,19 @@ import redis
 import argparse
 
 def centralize_to_target_db(target_dbname):
-    target_dbport = SonicDBConfig.get_port(target_dbname)
-    target_dbhost = SonicDBConfig.get_hostname(target_dbname)
+    target_dbport = SonicDBConfig.getDbPort(target_dbname)
+    target_dbhost = SonicDBConfig.getDbHostname(target_dbname)
 
-    dblists = SonicDBConfig.get_dblist()
+    dblists = SonicDBConfig.getDbList()
     for dbname in dblists:
-        dbport = SonicDBConfig.get_port(dbname)
-        dbhost = SonicDBConfig.get_hostname(dbname)
+        dbport = SonicDBConfig.getDbPort(dbname)
+        dbhost = SonicDBConfig.getDbHostname(dbname)
         # if the db is on the same instance, no need to move
         if dbport == target_dbport and dbhost == target_dbhost:
             continue
 
-        dbsocket = SonicDBConfig.get_socket(dbname)
-        dbid = SonicDBConfig.get_dbid(dbname)
+        dbsocket = SonicDBConfig.getDbSock(dbname)
+        dbid = SonicDBConfig.getDbId(dbname)
 
         r = redis.Redis(host=dbhost, unix_socket_path=dbsocket, db=dbid)
 
@@ -49,7 +49,7 @@ Example : centralize_database APPL_DB
     if args.target_db:
         try:
             centralize_to_target_db(args.target_db)
-            print(SonicDBConfig.get_instancename(args.target_db))
+            print(SonicDBConfig.getDbInst(args.target_db))
         except Exception as ex:
             template = "An exception of type {0} occurred. Arguments:\n{1!r}"
             message = template.format(type(ex).__name__, ex.args)