fix NDB() instantiation

PR: https://github.com/truenas/middleware/pull/7151

Fixes a few issues.

• `with pyroute2.NDB().interfaces...` opened a netlink socket and left it dangling every time an interface was up/down'ed

• NDB() is absurdly chatty (even only logging errors) and instantiating this class actually starts a thread which monitors kernel network events and will log lots of messages (repeatedly) to middlewared.log

• `service.start/stop kubernetes` is causing a golang core dump (unrelated problem upstream) however it showed these problems

Fix this by:

• instantiating a NDB() class on up()/down() respectively

• use the correct context manager inside the class object so the changes that are pushed to the interface actually take effect so when the method returns, it's fully complete

• turn off logging entirely and catch any exception

• ensure we always close the netlink socket