Including tasks has a performance penalty when compared with importing
tasks. If the include has a condition associated with it, then the
overhead of the include may be lower than the overhead of skipping all
imported tasks. For unconditionally included tasks, switching to
import_tasks provides a clear benefit.

Benchmarking of include vs. import is available at [1].

This change switches from include_tasks to import_tasks where there is
no condition applied to the include.

[1] https://github.com/stackhpc/ansible-scaling/blob/master/doc/include-and-import.md#task-include-and-import

Partially-Implements: blueprint performance-improvements

Change-Id: Ia45af4a198e422773d9f009c7f7b2e32ce9e3b97