Fixed comment length in cgroups tests.

This style issue started creeping up in other RR's Review bot feed back:

Error:
 Checking 426 files using filter --filter=-,+build/class,
+build/deprecated,+build/endif_comment,+runtime/vlog,
+whitespace/comma,+whitespace/ending_newline,+whitespace/forcolon,
+whitespace/indent,+whitespace/line_length,+whitespace/tab,
+whitespace/todo
src/tests/cgroups_tests.cpp:829:  Lines should be <= 80 characters
long  [whitespace/line_length] [2]
Total errors found: 1

Review: https://reviews.apache.org/r/21098
Extend the Linux launcher to use clone.

The launcher can now support clone'ing processes with namespace flags.

Review: https://reviews.apache.org/r/20816
Added DynamicLibrary to stout.

Addition of DynamicLibrary class to stout, to enable future plugins
inside of mesos.

Review: https://reviews.apache.org/r/21013
Fix for mesos fetcher not applying the executor bit.

Review: https://reviews.apache.org/r/21127
Updated tests to use a strict registry, by default.

Review: https://reviews.apache.org/r/20820
Enabled unbundled usage of http-parser.

Updates libprocess configure check for http-parser to build against
system dependencies outlined in MESOS-1071 + fixes libprocess local
'make check' which was broken.

Review: https://reviews.apache.org/r/20983
Adds Singularity to Mesos Frameworks page.
Cleaned up the logging level configuration.

Review: https://reviews.apache.org/r/20850
Documented Clock::settle.
MESOS-1310: Changed 'reply' to 'send' in slave registration.

Review: https://reviews.apache.org/r/21183
Refactored ZooKeeperImpl into ZooKeeperProcess.

See MESOS-1318 for more details.

Review: https://reviews.apache.org/r/21182
Fixed a bug with containerization in MesosTest.

Review: https://reviews.apache.org/r/21180
Added a test to ensure a recovered slave that does not re-register is removed.

Review: https://reviews.apache.org/r/21176
Added a test that ensure a recovered slave is not removed.

Review: https://reviews.apache.org/r/21186
Added a test to ensure a non-strict registry is write-only.

Review: https://reviews.apache.org/r/21189
Added user field to CommandInfo.

Enables individual executors and tasks to run as a specific user. If
the user field is present both in FrameworkInfo and here, the
CommandInfo user value takes precedence.

Review: https://reviews.apache.org/r/21167
Introduced a HealthCheck protobuf.

Review: https://reviews.apache.org/r/21052
Added an optional timeout to metrics collection.

Review: https://reviews.apache.org/r/21092
Updated post-reviews to catch exceptions and return None if ignoring
errors in execute.

Review: https://reviews.apache.org/r/21086
Fixed Protobuf to JSON serialization of optional fields with default values.

Previously, only optional fields which where explicitly set would be
serialized regardless whether default values was present.  This patch
adds those fields explicitly.

Review: https://reviews.apache.org/r/21246