[sonic-linkmgrd][202012] submodule update (#10270)

ca4b9a1 Guohan Lu Thu Mar 3 17:51:43 2022 -0800 [doc]: add lgtm badge in README.md
00c9b21 Longxiang Lyu Wed Mar 2 18:05:18 2022 +0800 Enable lgtm (#33)
3ae9be4 Longxiang Lyu Wed Mar 2 07:19:33 2022 +0800 Improve make clean (#32)
6997a1f Longxiang Lyu Wed Mar 9 10:03:00 2022 +0800 Add .clang-format file to format code (#28)
3368182 Jing Zhang Mon Mar 14 15:41:11 2022 -0700 Prevent switching MUX to "Unknown" (#36)