utils.process: Support timeout for "wait"

Our process library only allows to specify timeout for process execution
when used as the whole package using "run" method, but it might be
useful to allow the same kind of treatement for "wait". Let's move the
code there.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

avocado/utils/process.py

@@ -808,14 +808,47 @@ class SubProcess(object):
             self._fill_results(rc)
         return rc
 
-    def wait(self):
+    def wait(self, timeout=None, sig=signal.SIGTERM):
         """
         Call the subprocess poll() method, fill results if rc is not None.
+
+        :param timeout: Time (seconds) we'll wait until the process is
+                        finished. If it's not, we'll try to terminate it
+                        and get a status.
+        :param sig: Signal to send to the process in case it did not end after
+                    the specified timeout.
         """
+        def timeout_handler():
+            self.send_signal(sig)
+            self.result.interrupted = "timeout after %ss" % timeout
+
         self._init_subprocess()
-        rc = self._popen.wait()
-        if rc is not None:
-            self._fill_results(rc)
+        rc = None
+
+        if timeout is None:
+            rc = self._popen.wait()
+        elif timeout > 0.0:
+            timer = threading.Timer(timeout, timeout_handler)
+            try:
+                timer.start()
+                rc = self._popen.wait()
+            finally:
+                timer.cancel()
+
+        if rc is None:
+            stop_time = time.time() + 1
+            while time.time() < stop_time:
+                rc = self._popen.wait()
+                if rc is not None:
+                    break
+            else:
+                self.kill()
+                rc = self._popen.wait()
+
+        if rc is None:
+            # If all this work fails, we're dealing with a zombie process.
+            raise AssertionError('Zombie Process %s' % self._popen.pid)
+        self._fill_results(rc)
         return rc
 
     def stop(self):
@@ -868,36 +901,8 @@ class SubProcess(object):
         :returns: The command result object.
         :rtype: A :class:`CmdResult` instance.
         """
-        def timeout_handler():
-            self.send_signal(sig)
-            self.result.interrupted = "timeout after %ss" % timeout
-
         self._init_subprocess()
-
-        if timeout is None:
-            self.wait()
-        elif timeout > 0.0:
-            timer = threading.Timer(timeout, timeout_handler)
-            try:
-                timer.start()
-                self.wait()
-            finally:
-                timer.cancel()
-
-        if self.result.exit_status is None:
-            stop_time = time.time() + 1
-            while time.time() < stop_time:
-                self.poll()
-                if self.result.exit_status is not None:
-                    break
-            else:
-                self.kill()
-                self.poll()
-
-        # If all this work fails, we're dealing with a zombie process.
-        e_msg = 'Zombie Process %s' % self._popen.pid
-        assert self.result.exit_status is not None, e_msg
-
+        self.wait(timeout, sig)
         return self.result