In this commit, we add a makefile helper that can be used to add the
"-short" flag to the "go test" command when running unit tests via "make
unit ...".
Tests can then be expanded with a `testing.Short()` check to potentially
skip the test in short mode. This is useful for if a dev wants to
quickly run most of the tests in a package but would like to opt out of
running the longer form tests such as stress tests or rapid generation
tests.
This commit adds this check to two graph/db tests.