bump version to 1.13.1-rc2

Signed-off-by: Victor Vieux <victorvieux@gmail.com>

bump version to 1.13.0-rc7

Signed-off-by: Victor Vieux <vieux@docker.com>

Merge pull request moby#71 from mlaventure/bump-1.12.6

Bump version to 1.12.6

Merge pull request moby#29466 from vieux/bump_1.12.5

bump to 1.12.5

Merge pull request moby#29424 from tonistiigi/fix-sdin-close

Fix race on sending stdin close event