[autotest] Enable log_diff for server side test.

The bug was introduced when we try to force to collect all logs if a test
failed, refer to CL:
https://chromium-review.googlesource.com/#/c/174058

For server side test, the success flag does not pass to the code to run
log_after_each_test, thus all logs are collected by default.

The fix is to add a line of code in _sysinfo_after_test_script to pass the
flag mytest.success to the script to run on the dut.

Also update dummy_FailServer to be consistent on naming.

BUG=chromium:386242
TEST=test_that 172.22.30.146 dummy_PassServer
confirm only the log diff is collected:
/tmp/test_that_results_8Xj6Qj/results-1-dummy_PassServer/dummy_PassServer/sysinfo/var/log_diff/
test_that 172.22.30.146 dummy_FailServer
confirm the full log is collected:
/tmp/test_that_results_iAOAfZ/results-1-dummy_FailServer/dummy_FailServer/sysinfo/var/log/

Change-Id: Icec189c1c0d05ece11d41c68517b6671193a9cd9
Reviewed-on: https://chromium-review.googlesource.com/204488
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
diff --git a/server/test.py b/server/test.py
index 8fdba9d..c184d65 100644
--- a/server/test.py
+++ b/server/test.py
@@ -27,6 +27,9 @@
 import pickle
 from autotest_lib.client.bin import test
 mytest = test.test(job, '', %r)
+# success is passed in so diffable_logdir can decide if or not to collect
+# full log content.
+mytest.success = %s
 sysinfo_pickle = os.path.join(mytest.outputdir, 'sysinfo.pickle')
 if os.path.exists(sysinfo_pickle):
     job.sysinfo = pickle.load(open(sysinfo_pickle))
@@ -200,7 +203,7 @@
     def after_hook(self, mytest, host, at, outputdir):
         self._push_pickle(host, outputdir);
         # run the post-test sysinfo script
-        at.run(_sysinfo_after_test_script % outputdir,
+        at.run(_sysinfo_after_test_script % (outputdir, mytest.success),
                results_dir=self.job.resultdir)
 
         self._pull_sysinfo_keyval(host, outputdir, mytest)