Removed trailing diff/ from review line in commit message.

Review: https://reviews.apache.org/r/28205
Simplified label JSON modeling with JSON::Protobuf.

JSON fields doesn't need to be set explicitly, so label modeling can
be simplified with JSON::Protobuf.

Review: https://reviews.apache.org/r/28287
Allowed turning off network socket statistics collection.

Review: https://reviews.apache.org/r/28295
Added DiskInfo to the Resource protobuf.

Review: https://reviews.apache.org/r/27550
Fixed the tab issue in mesos.proto.
Removed unnecessary calls to Shutdown() in the reconciliation tests.

Review: https://reviews.apache.org/r/28265
Added a task reconciliation continuation for re-use in the Master.

Review: https://reviews.apache.org/r/28266
Updated killTask to perform reconciliation for unknown tasks.

Review: https://reviews.apache.org/r/28267
Changed master label test to strictly enforce format.

Review: https://reviews.apache.org/r/28293
Changed slave label test to strictly enforce format.

Review: https://reviews.apache.org/r/28294
Match future dispatch messages with type info.

Review: https://reviews.apache.org/r/28052
Fixed future dispatch in tests to match function type.

Review: https://reviews.apache.org/r/28081
Added option to force pull docker image.

Review: https://reviews.apache.org/r/28190
Fixed a few grammar mistakes in mesos.proto.
Silenced symbolic link to pre-commit in bootstrap.

Fixes MESOS-1960.

Review: https://reviews.apache.org/r/28303
Added validation for Resource objects with DiskInfo.

Review: https://reviews.apache.org/r/28258
Allowed C++ Resources to handle DiskInfo.

Review: https://reviews.apache.org/r/28264
Fixed a bug due to missing canonicalize.

Review: https://reviews.apache.org/r/28304
Added missed changes to DiskInfo patches..
Made libprocess generate valid HTTP.

While working on a pure Scala driver for Mesos, I discovered that
libprocess does not generate valid HTTP. It uses chunked encoding
combined with HTTP 1.0, which has only been added in HTTP
1.1. Additionally it stores the PID in the User-Agent field with an
incompatibe format ('@' and ':' are not allowed). This patch sets the
HTTP version to 1.1, adds an empty Host header (Host is mandatory in
1.1) and adds the Libprocess-From header. The User-Agent header is
left untouched for backwards compatibility reasons. Even strict HTTP
parser shouldn't error, but just ignore everything between the invalid
character and the CRLF.

Review: https://reviews.apache.org/r/27865