Add view builder to QoS specs API extension

Add view builder to QoS specs API extension

Add view builder for qos_specs.create(), index(), show() and associations()
to in order to make the response more easier to be consumed by client.

This patch also:
  fixed circular reference error when raising HTTP exception.
  fixed some typo in debug message and removed unused imports.

fix bug: # 1219016

Change-Id: I107888e6b4dac8eb5f1b45a87721a7b5efc45632