Increase start time to 20 seconds to avoid rare network failures

Older and slower versions of tor can't quite bootstrap in 15 seconds.
(At least on slow machines.)

README

@@ -89,9 +89,9 @@ HS Connection Tests:
 Waiting for the network:
 
   The tools/test-network.sh script waits CHUTNEY_START_TIME seconds
-  (default: 15) before calling chutney verify, because that's the minimum
+  (default: 20) before calling chutney verify, because that's the minimum
   amount of time it takes to bootstrap a consensus containing relays.
-  (It takes 5 seconds for the authorities to create the first consensus,
+  (It takes 5-10 seconds for the authorities to create the first consensus,
   then 10 seconds for relays to bootstrap, submit their descriptors, and be
   included in the next consensus.) If CHUTNEY_START_TIME is negative, the
   script leaves the network running, and exits immediately (without verifying).

tools/test-network.sh

@@ -177,11 +177,11 @@ fi
 cd "$CHUTNEY_PATH"
 ./tools/bootstrap-network.sh "$NETWORK_FLAVOUR" || exit 2
 
-# chutney starts verifying after 15 seconds, keeps on trying for 60 seconds,
+# chutney starts verifying after 20 seconds, keeps on trying for 60 seconds,
 # and then stops immediately (by default)
-# Even the fastest chutney networks take 5 seconds for their first consensus
+# Even the fastest chutney networks take 5-10 seconds for their first consensus
 # and then 10 seconds after that for relays to bootstrap and upload descriptors
-CHUTNEY_START_TIME=${CHUTNEY_START_TIME:-15}
+CHUTNEY_START_TIME=${CHUTNEY_START_TIME:-20}
 CHUTNEY_BOOTSTRAP_TIME=${CHUTNEY_BOOTSTRAP_TIME:-60}
 CHUTNEY_STOP_TIME=${CHUTNEY_STOP_TIME:-0}