Merge pull request tensorflow#10448 from av8ramit/rc2

Updating tag to 1.2.0-rc2.

Merge pull request tensorflow#10225 from gunan/relnotes

Announce upgrade to cuDNN 6.0.

Merge pull request tensorflow#10048 from av8ramit/cherrypicks

Seal learn_runner.

Merge pull request tensorflow#9351 from av8ramit/cherrypicks

TensorBoard Cherrypick

small change to format code (tensorflow#9223)

Merge pull request tensorflow#8958 from rohan100jain/branch_152141388

Branch 152141388

Update roadmap (tensorflow#8672)

Fixing 2 minor issues as suggested by Gunan.

Update release note.

Bump the version of nccl for macos fixes.