[autotest] Drop suite_min_duts keyval when creating suite job

This is part III of making host scheduler support a suite_min_duts
requirement per suite.

With this CL, the suite_min_duts is piped from run_suite
to the rpc method create_suite_job and dropped as a job keyval.

DEPLOY=apache
TEST=Run run_suite, confirm 'suite_min_duts' is dropped
as a job keyval of the suite in the db.
BUG=chromium:432652

Change-Id: I3193aba8c0938c3e8d7b3854c19b42c3f14e2829
Reviewed-on: https://chromium-review.googlesource.com/232570
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Fang Deng <fdeng@chromium.org>
Tested-by: Fang Deng <fdeng@chromium.org>
diff --git a/server/cros/dynamic_suite/constants.py b/server/cros/dynamic_suite/constants.py
index 7f2304a..c10f231 100644
--- a/server/cros/dynamic_suite/constants.py
+++ b/server/cros/dynamic_suite/constants.py
@@ -10,6 +10,8 @@
 # Job keyval indicating whether a job is for an experimental test.
 JOB_EXPERIMENTAL_KEY = 'experimental'
 RETRY_ORIGINAL_JOB_ID = 'retry_original_job_id'
+# Job keyval indicating the minimum duts required by the suite
+SUITE_MIN_DUTS_KEY = 'suite_min_duts'
 
 # Job attribute and label names
 EXPERIMENTAL_PREFIX = 'experimental_'