test: test job for randtrimwrite

test: test job for randtrimwrite

This test exposes a problem with randtrimwrite when norandommap is
enabled.

Currently we check to see if the last write and last trim ended at the
same position. If so, we decide that the next operation should be a
trim. This is ok in most cases but if norandommap is enabled, it could
happen by chance that we just finished a trim + write on an offset and
randomly chose that same offset again. This would fool fio into thinking
that it already finished a trim + write pair when it actually issued
only a trim operation.

Signed-off-by: Vincent Fu <vincent.fu@samsung.com>