Add ruby 2.1.2 to bosh-blobstore-client/Dockerfile
Add ruby 2.1.2 to bosh-blobstore-client/Dockerfile

- This is to support 263 and 262 pipelines

[#152849538](https://www.pivotaltracker.com/story/show/152849538)

Signed-off-by: Jamil Shamy <1a6c312d8b7ebde5d54d0b4f1a4353b7c149e3bf@pivotal.io>

barthy1/bosh,barthy1/bosh,barthy1/bosh,barthy1/bosh