microkernel: lock interrupts in _k_state_bit_[re]set()

Locks interrupts in the microkernel routines _k_state_bit_reset() and
_k_state_bit_set(). This is a necessary pre-requisite for allowing
microkernel objects to pend on nanokernel objects since that feature
will require the manipulation of the microkernel queues in the context
of an ISR as well as the kernel server fiber.

Change-Id: I2d263707e0d3aed75bba971df878daa3d7ae1d11
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>