Fix Travis CI failure of multiple_merges_during_fold_test

The environment that Travis runs test under unfortunately does not
immediately pick up the expected number of files to merge for the
different merge operations in the multiple_merges_during_fold_test.
This commit changes the test to re-try merging until the expected
result is seen (or eventually have the test timeout).
Move include_lib for EUnit inside -ifdef(TEST)
Fix EUnit timeout mismatch in bitcask_qc_fsm.erl
Merge pull request #74 from basho/jdb-fix-travis-failure

Fix Travis CI failure of multiple_merges_during_fold_test

After many intermittent timing failures over in TravisCI land, we have this:

    BUILD PASSED: [bitcask jdb-fix-travis-failure:771c92d] by Scott Lystig Fritchie https://travis-ci.org/basho/bitcask/builds/5266676