tests/_runner.lua: Use less waiting

Before this, the test runner used a timer which fired every 0.1 seconds
to "do its thing". Many of these waits seem unnecessary.

This commit makes the test runner wait 0 seconds for the first call of a
step function. Only following calls will have a timeout of 0.1 seconds
applied.

A full run of the test suite (tests/run.sh without further arguments)
took about 100 seconds before this change. After this change, we are
down to 60 seconds. This is almost factor two faster! (Well, five thirds
is the exact number, so factor 1.66)

(The numbers are best out of three runs. The "before" number is rounded
down while the "after" number is rounded up.)

Signed-off-by: Uli Schlachter <psychon@znc.in>

tests/_runner.lua

@@ -32,7 +32,7 @@ end)
 runner.run_steps = function(steps)
     -- Setup timer/timeout to limit waiting for signal and quitting awesome.
     -- This would be common for all tests.
-    local t = timer({timeout=0.1})
+    local t = timer({timeout=0})
     local wait=20
     local step=1
     local step_count=0
@@ -64,6 +64,7 @@ runner.run_steps = function(steps)
                 step = step+1
                 step_count = 0
                 wait = 5
+                t.timeout = 0
                 t:again()
                 return
             end
@@ -78,6 +79,7 @@ runner.run_steps = function(steps)
         else
             wait = wait-1
             if wait > 0 then
+                t.timeout = 0.1
                 t:again()
             else
                 io.stderr:write("Error: timeout waiting for signal in step "