Fix VLOGs being disabled (#2509)
Our TF_VLOGs had been disabled due to a conflict between
`TF_CPP_MIN_LOG_LEVEL` and TF_VLOG since TF_VLOG logs with tf::INFO,
which ends up getting logged nowhere since because of this check:
https://github.com/tensorflow/tensorflow/blob/efff893c709b585da9771cb3a2997321efef36ae/tensorflow/core/platform/default/logging.cc#L195
