Check for previous builds at import.
Check for previous builds at import.

  * This is done to make sure we are not importing new build
    documents when we already parsed them.

Change-Id: Ia57d49aa7f511c4958ab21bcd000e9c2e14a6497

joyxu/kernelci-backend,kernelci/kernelci-backend,kernelci/kernelci-backend,joyxu/kernelci-backend,joyxu/kernelci-backend