Fix net_unittests on Android swarming by adding testserver as a data_dep

TBR=phajdan.jr
BUG=589318

Review URL: https://codereview.chromium.org/1914073002

Cr-Commit-Position: refs/heads/master@{#389844}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index c6f80de2..949e03ae 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -317,6 +317,7 @@
 
 _ANDROID_SPECIFIC_PYDEPS_FILES = [
     'build/android/test_runner.pydeps',
+    'net/tools/testserver/testserver.pydeps',
 ]
 
 _GENERIC_PYDEPS_FILES = [