Always create o-a-c's $TEMPLATE_ROOT

Creating $TEMPLATE_ROOT is common to both os-apply-config package and
source installs, so move it into it's own install hook script under
install.d.

Change-Id: Iba79129cd111c144f67efabb93d4eb81641d1c2c
Merge "Always create o-a-c's $TEMPLATE_ROOT"