[ZEPPELIN-3080] Removing duplicate Date header

[sjoerdmulder]

What is this PR for?

Removing the duplicate Date header that is also in the wrong format according to the RFC, currently every request contains the following headers (using curl -I)

HTTP/1.1 200 OK
Date: Monday, November 27, 2017 3:20:42 PM UTC
Access-Control-Allow-Credentials: true
Access-Control-Allow-Headers: authorization,Content-Type
Access-Control-Allow-Methods: POST, GET, OPTIONS, PUT, HEAD, DELETE
X-FRAME-OPTIONS: SAMEORIGIN
X-XSS-Protection: 1
Content-Type: application/octet-stream
Date: Mon, 27 Nov 2017 15:20:42 GMT
Content-Length: 59
Server: Jetty(9.2.15.v20160210)

What type of PR is it?

Bug Fix

What is the Jira issue?

ZEPPELIN-3080

Questions:

• Does the licenses files need update?
  Nope
• Is there breaking changes for older versions?
  Nope
• Does this needs documentation?
  Nope

[sjoerdmulder]

@felixcheung finally got the build working :)

[jongyoul]

LGTM. BTW, is there any issue for the front side?

[sjoerdmulder]

I figured it out because we have a server side process (Spray client) doing health-checks and giving warnings about it:

Illegal response header: Illegal 'Date' header: Invalid input 'r', expected ", " or ' ' (line 1, pos 4):
Thursday, July 5, 2018 7:50:52 AM UTC
   ^

[Leemoonsoo]

LGTM