This variable must be executable, so using True won't work. Since
true is the default in finalise-tinyipa, remove the explicit setting
from the role.
Also remove this variable from build-tinyipa since it's not used there
and update the documentation accordingly.
Change-Id: Ibe744121b863ef1265e5e3ead7ab13fef0855fc6
1eee1c17a4