Bug 18364: [Follow-up] Also add an environment variable to prevent locking

Bug 18364: [Follow-up] Also add an environment variable to prevent locking

The test in SendCirculationAlert is extended by adding an env var
called KOHA_NO_TABLE_LOCKS. If this var is set to a true value,
the table locking is skipped too.

This is useful when running a test without prove. The variable could be
set in a shell profile.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Mason James <mtj@kohaaloha.com>
(cherry picked from commit 15751085e950b38df235d11e958259e15ef48f37)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>