Cannot open the database of a single user when a password is set.

The issue is quite heavy and the source hasn't been found yet. A current
workaround is to have all the user database set with no password.

Added a database closing statement to the end of every database request.

TODO: Check issue connecting to user databases.

Change-Id: Iea8bc3c9086c64a29d9692cdda86da13889bf514
Signed-off-by: Peter Merkert <p.merkert@sap.com>
Fixed a junit assertion expression to better fix JUnit guidlines.

Change-Id: I22849b0b34b2a3e10a65459d9f47d4f6925769b0
Signed-off-by: Peter Merkert <p.merkert@sap.com>
Added comment to UserPersistenceTest as the database connection can't be
closed there, because there is no connection open.

Change-Id: Ic6620991c9a65352562c7a71195ffef7dc047f08
Signed-off-by: Peter Merkert <p.merkert@sap.com>