[Submodule] Update sonic-swss-common (sonic-net#3770)

a4a1e10 - 2019-11-07 : Changes in swss-common submodule to support NAT feature. (sonic-net#304) [Kiran Kumar Kella]
b1375bb - 2019-10-28 : [consumer_table] Add messages for performing object availability query (sonic-net#314) [Danny Allen]
2fe2327 - 2019-10-25 : adding FDB table in CFG db (sonic-net#303) [anilkpandey]
2018880 - 2019-09-26 : added COUNTERS_LAG_NAME_MAP_TABLE in COUNTERS_DB [anilkpandey]
f41dcc3 - 2019-10-07 : added lua script to flush fdb entries [anilkpandey]
c87a7cf - 2019-10-25 : [consumer_table] Add messages for performing attribute enum value capabilities query (sonic-net#313) [Danny Allen]

Author: prsunny