[sonic-swss-common] Update submodule (#8344)

Includes below commits
```
e95a466 2021-08-04 | Fix: DBInterface::get() return nullable strings (#516) [Qi Luo]
f89b2ac 2021-07-29 | [netlink]refill netlink cache when failing to get the link object by name. (#506) [wangshengjun]
22b8715 2021-07-26 | Fix test_ConfigDBSubscribe timing risk (#512) [Qi Luo]
27dbcea 2021-07-26 | added missing headers for building with gcc-10.3 (#494) [Denis Pronin]
7f6ab6d 2021-07-25 | Modify the hardcode separator ":" to variable. (#473) [PJHsieh]
```

Author: qiluo-msft