Updated rootpath validation method in zookeeper coordinator

[cluyihunter]

Validate rootpath with Exists instead of Create to avoid 'zk: not authenticated' error.

[cluyihunter]

Hi @toddpalino, I tried to solve the issue by digging into the ACL part in samuel/go-zookeeper repo, and found that it does not currently support SASL authentication, where at least a username should be returned in AuthACL (see "https://ihong5.wordpress.com/tag/zookeeper-acl/"). I tried to modify Burrow and pass on SASL credentials using DigestACL but it didn't work. If anyone is interested in fixing the problem I am happy to help & learn. Thanks!

[coveralls]

Coverage increased (+0.07%) to 74.055% when pulling d96b1d1 on cluyihunter:master into 12e681a on linkedin:master.

[cluyihunter]

My apologies for all the messy small commits. I haven't figured out how to test build and coverage locally as I cannot get past the 'use of internal package is not allowed' restriction in Golang.

[maxtuzz]

@cluyihunter If you move your src over to ~/go/src/github.com/linkedin/Burrow then those errors should go away. Without this, you're technically using the same project as an external dependency which results in errors.

[cluyihunter]

@maxtuzz Yes I have github.com/linkedin/Burrow in src under my gopath, but still the error persists whenever I try testing (use of internal package is not allowed)