unified: Fix test_sema/microkernel

Fixes test_sema/microkernel so that the variable assigned the return
value from task_sem_group_take() is of type 'ksem_t' instead of 'int'.

Work by: Peter Mitsis <peter.mitsis@windriver.com>

Change-Id: Iee9f321a6bd51ca3bc0cd8b0c7eceae8a5bf7ce0
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>