Bug 12271: (follow-up) teach valid-templates.t how to include specified templates

Bug 12271: (follow-up) teach valid-templates.t how to include specified templates

Two of the template includes in the Bootstrap theme cannot be tested
all by themselves because they require that the template that includes
them define BLOCKs.  This patch ensures that they are excluded
from individual testing; they will get exercised sufficiently by being
including by all of the other Bootstrap templates.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit b97e691ef87bf3fd89f38ba0b1772d8fcac44b33)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>