twister: fix integration_platforms selection
twister: fix integration_platforms selection

Logic for selecting non-default platforms listed in
integration_platforms did not work. Functionality is restored in this
change.

Fixes #32835

Signed-off-by: Anas Nashif <0d9952ec84ac43c159f6b7e7ed99a9080c00dd6e@intel.com>

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