test_cloud_suite: the quiet wait's deadline is no longer the test

The cloud suite's host tests replay a print's log from threads, and the
suite's quiet wait gave up after 3 s (QUIET_TIMEOUT_S in setUp). On a
loaded host the last replayed lines landed after that, and a test failed
with "still running service moves after 3 s" instead of its own finding:
about one run of the module in five, a different test each time, alone
as well as under the full suite. The deadline is now 15 s. It is a
deadline and not a wait: a quiet machine is seen at once, so a passing
run is no slower. The one test that waits the deadline out on purpose (a
motion that never goes idle) sets 3 s for itself; tearDown puts the
module's value back.

Proof: before, test_cloud_suite failed 2 of 10 runs by itself, every
failure the quiet deadline (test_lid_during_button_wait_on_the_bench_excerpt,
test_pause_resume_fails_without_the_retraced_restart,
test_mode_switch_fails_when_gfhome_never_saw_the_head_move,
test_pause_resume_fails_when_the_kernel_refuses_the_resume). After, 10 of
10. forgetest's whole unit suite: 451 tests OK, 4 skipped, in 492 s
against 491 s before. A host-test change: no catalog consequence.

forgetest/tests/test_cloud_suite.py

@@ -185,7 +185,10 @@ class CloudSuiteTests(unittest.TestCase):
         self.engine_line = EFFECTIVE_LINE      # what the engine logs at the print; None = nothing
         self.client_limits = True              # the client names its header limits
         cloud.QUIET_S = 0.4
-        cloud.QUIET_TIMEOUT_S = 3
+        # A deadline, not a wait: a quiet machine is seen at once. The
+        # replays land their lines from threads, so under a loaded host a
+        # tighter deadline expires before the last of them is written.
+        cloud.QUIET_TIMEOUT_S = 15
         cloud.HUNT_TIMEOUT_S = 8
         self.script = None
 
@@ -556,6 +559,7 @@ class CloudSuiteTests(unittest.TestCase):
         self.append(fixture("huntlid"))
         # a motion in flight (never idle within the timeout) fails, and says so
         self.fc.state["status"]["state"] = "running"
+        cloud.QUIET_TIMEOUT_S = 3                   # this one waits the deadline out; tearDown puts it back
         self.assertFails(cloud.enter_cloud, "still running service moves")
 
     # -- the hunt with the lid open ------------------------------------------