Make use of current working dir explicit for compatibility with H2 1.4

H2 1.4 requires that file paths that are relative to the current
working directory declare this explicitly, i.e. the path
file:/some-dir must now be file:./some-dir.

This commit updates DatabaseTypeIntegrationTests to meet the
above-described requirement, thereby allowing the tests to pass when
run against H2 1.4.x.