Add arp perm rule & flush main ip route for container.

[Andrewmatilde]

For #2555,

1. in container the ip route changes caused by delete device will be late to some add route operation which will cause XXX exists and make all clear_bridge operations failed -> so I flush the main table before add routes.
2. in container the arp flooding speed is too slow , it will cost 10+mins to flooding all the arp rules -> so I add arp perm rules.

Test done on:

• [x] container
• [x] centos8.2
• [x] debian10.2