ACTS(wifi): Use shell command for setting country code

WifiManager.setCountryCode() is being removed, use the shell command to
set country code instead from ACTS tests.

Bug: 141107015
Test: Verified the changes
Change-Id: I23ebe57fcb8bed71b6b85ec1697e80bf150044f2
Merged-In: I23ebe57fcb8bed71b6b85ec1697e80bf150044f2
(cherry picked from commit 48df08cf90347b2419987942dd2f26bcd903585e)
diff --git a/acts/tests/google/wifi/WifiSensitivityTest.py b/acts/tests/google/wifi/WifiSensitivityTest.py
index 6e32e0e..c340756 100644
--- a/acts/tests/google/wifi/WifiSensitivityTest.py
+++ b/acts/tests/google/wifi/WifiSensitivityTest.py
@@ -408,7 +408,7 @@
             self.log.info('Already connected to desired network')
         else:
             wutils.reset_wifi(self.dut)
-            self.dut.droid.wifiSetCountryCode(
+            wutils.set_wifi_country_code(self.dut,
                 self.testclass_params['country_code'])
             testcase_params['test_network']['channel'] = testcase_params[
                 'channel']