Clean up yang-test to stop modifying source files during build.

In yang-test-plugin remove auto generated headers so that things
like timestamp changes will not be reported as changed files
after build.
Also move an artifact definition in commons pom and sal-binding-it
as enforced by the sort plugin.

Change-Id: I5d851d65c149611800a1f7418eb4b642e3fd8260
Signed-off-by: Tomas Olvecky <tolvecky@cisco.com>
Merge "Clean up yang-test to stop modifying source files during build."