Explicitly set retry limit to 0 in RunMockTests.

Environment variable "CHROMIUM_TEST_LAUNCHER_BOT_MODE"
will set retry limit to 3.
This causes RunMockTests test to retry failing and crashed tests.

Bug: 993323
Change-Id: If2ba3baa52a356b732bdc317171a3dc73ce306df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1752169
Commit-Queue: Ilia Samsonov <isamsonov@google.com>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686480}

base/test/launcher/test_launcher_unittest.cc

@@ -689,6 +689,7 @@ TEST_F(UnitTestLauncherDelegateTester, RunMockTests) {
   FilePath path = dir.GetPath().AppendASCII("SaveSummaryResult.json");
   command_line.AppendSwitchPath("test-launcher-summary-output", path);
   command_line.AppendSwitch("gtest_also_run_disabled_tests");
+  command_line.AppendSwitch("--test-launcher-retry-limit=0");
 #if defined(OS_WIN)
   // In Windows versions prior to Windows 8, nested job objects are
   // not allowed and cause this test to fail.