util/net: Place death tests into a *DeathTest test case

util/net: Place death tests into a *DeathTest test case.

Not doing this causes gtest to issue these warnings:

[WARNING] ../../third_party/gtest/gtest/src/gtest-death-test.cc:825::
Death tests use fork(), which is unsafe particularly in a threaded
context. For this test, Google Test detected 4 threads.

The gtest documentation recommends giving the test case a name ending in
DeathTest. Test cases named according to this convention run before all
other tests. Other death tests in Crashpad also follow this convention.

https://code.google.com/p/googletest/wiki/AdvancedGuide#Death_Tests_And_Threads

TEST=util_test HTTPMultipartBuilderDeathTest.*
R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/486429e4f4da4a1b54e07acd89abb99e2330da4d

[Mark Mentovai, 2014-10-31 19:00:02]

mark@chromium.org changed reviewers:
+ rsesek@chromium.org

[Robert Sesek, 2014-10-31 19:22:29]

LGTM

[Mark Mentovai, 2014-10-31 19:39:20]

Committed patchset #1 (id:1) manually as
486429e4f4da4a1b54e07acd89abb99e2330da4d (presubmit successful).