Bluetooth: Mesh: LPN: Fix clearing pending request
Bluetooth: Mesh: LPN: Fix clearing pending request

The code would unconditionally clear sent_req in update_timeout(),
which would e.g. cause us to switch to Friend Polls if the Friend
didn't respond to a Subscription List Add/Remove on the first attempt.

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

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