Bluetooth: Mesh: Fix typo when iterating GATT clients
Bluetooth: Mesh: Fix typo when iterating GATT clients

The intention of the code was to access client->conn and not
clients->conn (which would always access the first client struct).

Fixes #4738

Signed-off-by: Johan Hedberg <628991c7b0a19c384f9b99c21ec330ce952bb838@intel.com>

mbolivar/zephyr,nashif/zephyr,galak/zephyr,explora26/zephyr,zephyriot/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,explora26/zephyr,punitvara/zephyr,explora26/zephyr,galak/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,kraj/zephyr,punitvara/zephyr,Vudentz/zephyr,ldts/zephyr,Vudentz/zephyr,finikorg/zephyr,aceofall/zephyr-iotos,finikorg/zephyr,mbolivar/zephyr,aceofall/zephyr-iotos,zephyriot/zephyr,zephyrproject-rtos/zephyr,aceofall/zephyr-iotos,explora26/zephyr,ldts/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,punitvara/zephyr,galak/zephyr,zephyriot/zephyr,aceofall/zephyr-iotos,mbolivar/zephyr,finikorg/zephyr,nashif/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,ldts/zephyr,mbolivar/zephyr,nashif/zephyr,explora26/zephyr,galak/zephyr,nashif/zephyr,punitvara/zephyr,kraj/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,aceofall/zephyr-iotos,Vudentz/zephyr,zephyriot/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr,ldts/zephyr