[202205] Fix epoll and socket resource leak issue. (#651)

[kpetremann]

Cherry-picking this #651 for 202205 branch.

Why I did it

Fix epoll and socket resurce leak issue:
[chassis] Too many open files error and unable to connect to redis socket error sonic-net/sonic-buildimage#10870

The reason of this issue is in SWIG any method return a new object need decorate with %newobject, so SWIG will generate code to release C++ object when python wrapper object released: https://www.swig.org/Doc4.0/SWIGDocumentation.html#Customization_ownership

How I did it

Update swsscommon.i to decorate return new object methods with %newobject

How to verify it

Pass all test case.

Run following code in python and validate there is no epoll and socket leak:

from swsscommon.swsscommon import SonicDBConfig
from swsscommon.swsscommon import SonicV2Connector import gc

SonicDBConfig.load_sonic_global_db_config()
SonicDBConfig.get_ns_list()
db = SonicV2Connector(use_unix_socket_path=True, namespace='') db.connect("CONFIG_DB")
db.get_redis_client("CONFIG_DB")
client = db.get_redis_client("CONFIG_DB")
client.pubsub()
client.pubsub()
client.pubsub()
client.newConnector(0)
client.newConnector(0)
client.newConnector(0)

gc.collect()

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205

Description for the changelog

Fix epoll and socket resurce leak issue:
[chassis] Too many open files error and unable to connect to redis socket error sonic-net/sonic-buildimage#10870

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)