[autotest] Remove per-tick process restriction.

The per-tick process restriction was causing a performance problem
when a tick took a long time, and there isn't a good reason to keep
the per-tick process constraint as there is already a total process
constraint.

TEST=Ran the scheduler.  The unit tests pass.
BUG=chromium:471352

Change-Id: I2b669fb758fbcc898e1727da51bd6d4cd99cd5d2
Reviewed-on: https://chromium-review.googlesource.com/265072
Trybot-Ready: Paul Hobbs <phobbs@google.com>
Tested-by: Paul Hobbs <phobbs@google.com>
Commit-Queue: Paul Hobbs <phobbs@google.com>
Reviewed-by: Fang Deng <fdeng@chromium.org>
diff --git a/scheduler/scheduler_config.py b/scheduler/scheduler_config.py
index 8396909..63e4589 100644
--- a/scheduler/scheduler_config.py
+++ b/scheduler/scheduler_config.py
@@ -10,7 +10,6 @@
     FIELDS = [
                 ('max_processes_per_drone', int),
                 ('max_processes_warning_threshold', float),
-                ('max_processes_started_per_cycle', int),
                 ('clean_interval_minutes', int),
                 ('max_parse_processes', int),
                 ('tick_pause_sec', float),
@@ -28,6 +27,10 @@
 
 
     def read_config(self):
+        """
+        Reads the attributes (listed in `FIELDS`) from the global config
+        and copies them into self.
+        """
         config = global_config.global_config
         config.parse_config_file()
         for field, data_type in self.FIELDS: