Handle the choice of reboot of the instance in osutils.set_host_name

Since the sethostname plugin was moved in plugins.common, there was a bit
of Windows specific functionality inside it, the fact that it returns reboot_required
in order to set the hostname on Windows. Now this choice is moved to
osutils.set_host_name, which will simply return False for non-Windows systems.

Change-Id: Ic7774f2c7dd86f3ade82a19520df4301bc9674a7

cloudbaseinit/osutils/windows.py

@@ -466,6 +466,7 @@ class WindowsUtils(base.BaseOSUtils):
             six.text_type(new_host_name))
         if not ret_val:
             raise exception.CloudbaseInitException("Cannot set host name")
+        return True
 
     def get_network_adapters(self):
         """Return available adapters as a list of tuples of (name, mac)."""

cloudbaseinit/plugins/common/sethostname.py

@@ -63,7 +63,6 @@ class SetHostNamePlugin(base.BasePlugin):
             reboot_required = False
         else:
             LOG.info("Setting hostname: %s" % new_host_name)
-            osutils.set_host_name(new_host_name)
-            reboot_required = True
+            reboot_required = osutils.set_host_name(new_host_name)
 
         return (base.PLUGIN_EXECUTION_DONE, reboot_required)

cloudbaseinit/tests/osutils/test_windows.py

@@ -466,7 +466,7 @@ class TestWindowsUtils(unittest.TestCase):
             self.assertRaises(exception.CloudbaseInitException,
                               self._winutils.set_host_name, 'fake name')
         else:
-            self._winutils.set_host_name('fake name')
+            self.assertTrue(self._winutils.set_host_name('fake name'))
 
         mock_SetComputerNameExW.assert_called_with(
             self._winutils.ComputerNamePhysicalDnsHostname,

cloudbaseinit/tests/plugins/common/test_sethostname.py

@@ -52,6 +52,7 @@ class SetHostNamePluginPluginTests(unittest.TestCase):
             mock_service.get_host_name.return_value = None
 
         mock_get_os_utils.return_value = mock_osutils
+        mock_get_os_utils.return_value.set_host_name.return_value = True
 
         if hostname_exists is True:
             length = sethostname.NETBIOS_HOST_NAME_MAX_LEN