Merge ~wgrant/launchpad:preflight-10s into launchpad:master

[William Grant]

Wait longer in preflight.py for connections to die

Despite the comment saying it could wait for 10s, it in fact only waited
for up to 2s. This has for some time not been reliably sufficient, as
a rerun of full-update has often been necessary.

[Colin Watson (cjwatson)]

review: Approve

diff --git a/database/schema/preflight.py b/database/schema/preflight.py
index 6bf1abb..0a4053c 100755
--- a/database/schema/preflight.py
+++ b/database/schema/preflight.py
@@ -337,9 +337,9 @@ class KillConnectionsPreflight(DatabasePreflight):
 
         System users are defined by SYSTEM_USERS.
         """
-        # We keep trying to terminate connections every 0.5 seconds for
+        # We keep trying to terminate connections every 0.1 seconds for
         # up to 10 seconds.
-        num_tries = 20
+        num_tries = 100
         seconds_to_pause = 0.1
         if self.replication_paused:
             nodes = set([self.lpmain_master_node])