Merge pull request #287 from alena1108/jan3

 Use go 1.9.0

Merge pull request #286 from alena1108/dec31

Update golint and go version

reuse transport connection

Do not delete rancher-agent container

showing correct imagePull error

add params to support skip the nameserver check

Don't use mixedCase in package name

This is now a rule in golint

Merge pull request #272 from ibuildthecloud/master

Import cluster logic

Merge pull request #272 from ibuildthecloud/master

Import cluster logic

fix race condition when umounting

this part of code raise a race condition, where previous container start
failed and call unmount, where after the next container starts and
unmount removes the mount entry.(gc takes 1 second after calling unmount).
We don't need to call umount in this case as the gc will always run if container
is being removed  which gc thread will clean unused mount entries.