tests: Fix some compile errors and warnings

tests: Fix some compile errors and warnings

* aspath_test.c: match changes in aspath_unintern. Fix printf size_t warning.
* bgp_capability_test.c: compile warnings.
* bgp_mp_attr_test.c: update for attr parser context struct
* ecommunity_test.c: ecommunity_free/ecommunity
* test-checksum.c: some unused vars and funcs without need of prototypes.