this commit changes how the dockertest image is built.
it moves the command into dockertest/Makefile. It also
uses a cached file that -- if removed with make clean
-- can signal whether the image should be rebuilt.
(it may be ideal to have it either detect code has
changed, or just rebuild every time. )
Now 'make test' will run the go tests with option -test.short
and the sharness tests without any option.
And 'make test_expensive' will run the go tests without any
option and the sharness tests with option TEST_EXPENSIVE=1.
This should help fix the first part of issue #283.
License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
