msync/msync03.c: add EBUSY test for msync(2)

Merge msync03.c, msync04.c, msync05.c into one msync03
test, which contains EINVAL and ENOMEM error value tests.

And add new EBUSY error value test.

Signed-off-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>