Try to fix reboot problem in Perf tests by killing and starting the adb server.

Author: vhristov5555

core/device/helpers/adb.py

@@ -407,3 +407,17 @@ def reboot_device(device_id):
         output = Adb.run(command=command, device_id=device_id)
         assert '' in output, 'Failed to reboot the device.Error:' + output
         print 'Reboot started successfully.'
+
+    @staticmethod
+    def kill_server():
+        command = 'kill-server'
+        output = run(ADB_PATH + ' ' + command)
+        assert '' in output, 'Failed to kill server the device.Error:' + output
+        print 'Kill server successfully.'
+
+    @staticmethod
+    def start_server():
+        command = 'start-server'
+        output = run(ADB_PATH + ' ' + command)
+        assert 'daemon started successfully' in output, 'Failed to start the server.Error:' + output
+        print 'Start server successfully.'

tests/perf/start_time.py

@@ -181,6 +181,8 @@ def test_start_time(self, demo, config, device_name, device_id, first_start, sec
             second_start_expected = second_start
             Adb.reboot_device(self.DEVICE_ID)
             Emulator.wait(self.DEVICE_ID)
+            Adb.kill_server()
+            Adb.start_server()
 
         start_time_actual = 0
         second_start_actual = 0