Add a --bulkload option

[fzzzy]

We'd like to use this script to load up some expired records for testing the purge_ttl script on stage. I have a patch, but it needs to be cleaned up and turned into an option instead of being hardcoded.

diff --git a/loadtest.py b/loadtest.py
index 867b579..dbbd143 100644
--- a/loadtest.py
+++ b/loadtest.py
@@ -20,7 +20,7 @@ _WEIGHTS = {'metaglobal': [40, 60, 0, 0, 0],
             'post_count_distribution': [67, 18, 9, 4, 2],
             'delete_count_distribution': [99, 1, 0, 0, 0]}
 
-_PROBS = {'get': .1, 'post': .2, 'deleteall': 0.01}
+_PROBS = {'get': 0, 'post': 1, 'deleteall': 0}
 _COLLS = ['bookmarks', 'forms', 'passwords', 'history', 'prefs']
 _BATCH_MAX_COUNT = 100
 
@@ -103,7 +103,7 @@ async def test(session):
     if should_do('post'):
         cid = str(get_num_requests('distribution'))
         url = "/storage/clients"
-        wbo = {'id': 'client' + cid, 'payload': cid * 300}
+        wbo = {'id': 'client' + cid, 'payload': cid * 300, 'ttl': 1}
         data = json.dumps([wbo])
         resp, result = await storage.post(url, data=data, statuses=(200,))
         assert len(result["success"]) == 1, "No success records"
@@ -153,7 +153,7 @@ async def test(session):
             token = storage.auth_token.decode('utf8')
             payload_chunks = int((payload_length / len(token)) + 1)
             payload = (token * payload_chunks)[:payload_length]
-            wbo = {'id': id, 'payload': payload}
+            wbo = {'id': id, 'payload': payload, 'ttl': 1}
             data.append(wbo)
 
         data = json.dumps(data)