Upgrade jetty to 9.3.18.v20170406
Upgrade jetty to 9.3.18.v20170406

This version includes minor bug fixes. See the release notes [1] for
details.

[1] https://github.com/eclipse/jetty.project/releases/tag/jetty-9.3.18.v20170406

Change-Id: I6d455fe59647d1764c60b73ebff4ee6c27b68628

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