Hygiene: upgrade OkHttp libs to v2.6.0
Hygiene: upgrade OkHttp libs to v2.6.0

From the release notes[0]:

> Fix: Don't throw when converting an HttpUrl to a java.net.URI.
  Previously URLs with special characters like | and [ would break when
  subjected to URI’s overly-strict validation.
This fix may ease T120415.

[0] https://github.com/square/okhttp/blob/master/CHANGELOG.md#version-260

Change-Id: I0342d813d0fd52ffcb2986195a97d3143840bc68

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