Only import the sample data packs on tests that need them

Not all of our test cases really require the sample data packs,
and we are better off not using them because its hard to see exactly
what condition a test is testing when looking only at the Java code.
Clarify the dependency by only making the packs available when
there is a real need for it.

Change-Id: Id8a76ee7ee1f7efba585be4bed19a8fb5b3b3585
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>