Avoid concurrency problems

git-svn-id: http://h2database.googlecode.com/svn/trunk@5400 e6896862-9d19-0410-bfb3-e9fa5d50e656
Don't create a *.h2.db file when using the MVStore

git-svn-id: http://h2database.googlecode.com/svn/trunk@5401 e6896862-9d19-0410-bfb3-e9fa5d50e656
Disable test for in-memory databases

git-svn-id: http://h2database.googlecode.com/svn/trunk@5402 e6896862-9d19-0410-bfb3-e9fa5d50e656
Disable test for in-memory databases

git-svn-id: http://h2database.googlecode.com/svn/trunk@5403 e6896862-9d19-0410-bfb3-e9fa5d50e656