[autotest] Stop passing flags directly to lucifer

Passing flags directly through to lucifer is confusing, since some
flags come from job_reporter, some come from monitor_db.

This adds some redundant argument parsing to job_reporter, but is much
easier to grok.

Move -autotestdir, -watcherpath, and -resultsdir first.  Gathering has
its own flags, migrate those later.

BUG=chromium:810141
TEST=None

Change-Id: Ic716bdabfa97e8f1fe024924ff62551af1dc7ec9
Reviewed-on: https://chromium-review.googlesource.com/920921
Commit-Ready: Allen Li <ayatane@chromium.org>
Tested-by: Allen Li <ayatane@chromium.org>
Reviewed-by: Allen Li <ayatane@chromium.org>
diff --git a/venv/lucifer/autotest.py b/venv/lucifer/autotest.py
index e05eb24..60f984e 100644
--- a/venv/lucifer/autotest.py
+++ b/venv/lucifer/autotest.py
@@ -31,8 +31,8 @@
 
 import autotest_lib
 
-_AUTOTEST_DIR = autotest_lib.__path__[0]
-_SITEPKG_DIR = os.path.join(_AUTOTEST_DIR, 'site-packages')
+AUTOTEST_DIR = autotest_lib.__path__[0]
+_SITEPKG_DIR = os.path.join(AUTOTEST_DIR, 'site-packages')
 _SYSTEM_PYTHON = '/usr/bin/python2.7'
 
 _setup_done = False
@@ -105,7 +105,7 @@
 
     # drone_utility uses this.
     common = importlib.import_module('autotest_lib.scheduler.common')
-    common.autotest_dir = _AUTOTEST_DIR
+    common.autotest_dir = AUTOTEST_DIR
 
 
 def _system_site_packages():