tests: net: context: Fix invalid address family test
tests: net: context: Fix invalid address family test

The test had hard coded address family with value 4. This test
was failing as we have now AF_CAN family with value 4. Use 99
as an invalid address family value instead.

Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

GiulianoFranchetto/zephyr,finikorg/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,ldts/zephyr,ldts/zephyr,Vudentz/zephyr,galak/zephyr,ldts/zephyr,finikorg/zephyr,explora26/zephyr,explora26/zephyr,explora26/zephyr,galak/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,Vudentz/zephyr,ldts/zephyr,galak/zephyr,explora26/zephyr,nashif/zephyr,galak/zephyr