[sonic-swss-common] Update submodule

Includes commits:

```
2f79bb4 2021-01-16 | Fix ConfigDBPipeConnector.get_config() implementation (sonic-net#446) [Qi Luo]
fc64e3a 2021-01-12 | [dbconnector] protect db information with mutex (sonic-net#423) [Ying Xie]
e8a03de 2021-01-12 | [ci]: use sonicbld pool (sonic-net#445) [lguohan]
```