recycle SmVisitorTest for unit test

i.e. move unused SmVisitorTest to qa/ as MockVisitor, and
call it in existing test cases.

Change-Id: I20dc45537f7a0e325e952724607e695f3b3da21f
Reviewed-on: https://gerrit.libreoffice.org/13165
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>