Turn screen off during some tests to conserve battery power

This CL turns off the screen at the beginning of the tests in cases
where the screen need not be on.

Test: Done
Bug: None

Change-Id: I1000547dca68791c02287e4b65e6f02b27fa9275
Signed-off-by: Omar El Ayach <oelayach@google.com>
diff --git a/acts/tests/google/wifi/WifiSensitivityTest.py b/acts/tests/google/wifi/WifiSensitivityTest.py
index 0e5a9ac..be741d0 100644
--- a/acts/tests/google/wifi/WifiSensitivityTest.py
+++ b/acts/tests/google/wifi/WifiSensitivityTest.py
@@ -134,7 +134,7 @@
         This function initializes hardwares and compiles parameters that are
         common to all tests in this class.
         """
-        self.client_dut = self.android_devices[-1]
+        self.dut = self.android_devices[-1]
         req_params = [
             'RetailAccessPoints', 'sensitivity_test_params', 'testbed_params',
             'RemoteServer'
@@ -357,21 +357,26 @@
         Args:
             testcase_params: dict containing AP and other test params
         """
+        # Check battery level before test
+        if not wputils.health_check(self.dut, 10):
+            asserts.skip('Battery level too low. Skipping test.')
+        # Turn screen off to preserve battery
+        self.dut.go_to_sleep()
         band = self.access_point.band_lookup_by_channel(
             testcase_params['channel'])
-        wutils.reset_wifi(self.client_dut)
-        self.client_dut.droid.wifiSetCountryCode(
+        wutils.reset_wifi(self.dut)
+        self.dut.droid.wifiSetCountryCode(
             self.testclass_params['country_code'])
         self.main_network[band]['channel'] = testcase_params['channel']
         wutils.wifi_connect(
-            self.client_dut,
+            self.dut,
             self.main_network[band],
             num_of_tries=5,
             check_connectivity=False)
-        self.dut_ip = self.client_dut.droid.connectivityGetIPv4Addresses(
+        self.dut_ip = self.dut.droid.connectivityGetIPv4Addresses(
             'wlan0')[0]
         atten_dut_chain_map = wputils.get_atten_dut_chain_map(
-            self.attenuators, self.client_dut, self.ping_server, self.dut_ip)
+            self.attenuators, self.dut, self.ping_server, self.dut_ip)
         for idx, atten in enumerate(self.attenuators):
             if atten_dut_chain_map[idx] == testcase_params['attenuated_chain']:
                 atten.offset = atten.instrument.max_atten