tests: net: mld: Update after solicited-node mcast refactor.
tests: net: mld: Update after solicited-node mcast refactor.

1. MLD events now can happen before the test starts to run, (at iface
initialization time), so use static initialization of test semaphore.
2. Don't use a well-known multicast group like ff02::1 (all nodes),
as they are managed by the underlying stack. Use a dedicated test
address (ff10::1 here).

Signed-off-by: Paul Sokolovsky <35cb557f011771c94f127d6fef99f804b62203f5@linaro.org>

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