test:test51 add a few more tests for calling setcontext.
test:test51 add a few more tests for calling setcontext.

Change-Id: I272ac01c77537b80bab328aae1acd7b6ce6027fb

veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi