[bradh352]: use sonic-mgmt-common fork

update

Author: bradh352

.gitmodules

@@ -79,7 +79,8 @@
 	branch = master
 [submodule "src/sonic-mgmt-common"]
 	path = src/sonic-mgmt-common
-	url = https://github.com/sonic-net/sonic-mgmt-common.git
+	url = https://github.com/bradh352/sonic-mgmt-common.git
+	branch = bradh352/libyang3
 [submodule "src/wpasupplicant/sonic-wpa-supplicant"]
 	path = src/wpasupplicant/sonic-wpa-supplicant
 	url = https://github.com/sonic-net/sonic-wpa-supplicant.git