Add unique builds booted count.
Add unique builds booted count.

  * In the "Tested" string in the email, add the count of
    unique defconfigs boot tested compared to the total number
    of defconfigs built.

Change-Id: I6184657b027d0963a459f711261f2b1443b0216d

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