Bluetooth: L2CAP: Fix data leaks when segment cannot be sent
Bluetooth: L2CAP: Fix data leaks when segment cannot be sent

Now that bt_l2cap_send_cb can fail the buffer state needs to be save
and restored otherwise the data stored on it would be lost.

Signed-off-by: Luiz Augusto von Dentz <8530c5ea66a1bdbc08f98bfcf183c8be901b5990@intel.com>

galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,nashif/zephyr,nashif/zephyr,finikorg/zephyr