To show the community list of this attribute entry.
If the community list is an NULL string that means an empty list, then
the community is INTERNET. A number from 1 to 0xFFFFFFFF.
This integer number is represented by 4 OCTETs.
In the community list, it could have some Well-known numbers such as:
BGP_COMMUNITY_ATTRIBUTE_NO_EXPORT 0xFFFFFF01
BGP_COMMUNITY_ATTRIBUTE_NO_ADVERTISE 0xFFFFFF02