Fix python3 utf-8 decode issue and typo while creating app_monitor

This change corrects the input for ast.literal_eval()
and also corrects the variable (zapi.URL) called in
zabbix_api.py and zabbix.py.

From the Python3 documentation for ast.literal_eval():
Safely evaluate an expression node or a string containing
a Python expression. The string or node provided may
only consist of the following Python literal structures:
strings, numbers, tuples, lists, dicts, booleans, and None.

Change-Id: I710feff170cb464371d76ef3ee52392fa818c18d
Related-Bug: #1898515
Closes-Bug: #1898526

tacker/vnfm/monitor.py

@@ -232,7 +232,8 @@ class VNFAppMonitor(object):
 
     def _create_app_monitoring_dict(self, dev_attrs, mgmt_ip_address):
         app_policy = 'app_monitoring_policy'
-        appmonitoring_dict = ast.literal_eval(dev_attrs[app_policy])
+        appmonitoring_dict = ast.literal_eval(
+            dev_attrs[app_policy].decode('utf-8'))
         vdulist = appmonitoring_dict['vdus'].keys()
 
         for vduname in vdulist:
@@ -242,7 +243,7 @@ class VNFAppMonitor(object):
 
     def create_app_dict(self, context, vnf_dict):
         dev_attrs = vnf_dict['attributes']
-        mgmt_ip_address = vnf_dict['mgmt_ip_address']
+        mgmt_ip_address = vnf_dict['mgmt_ip_address'].decode("utf-8")
         return self._create_app_monitoring_dict(dev_attrs, mgmt_ip_address)
 
     def _invoke(self, driver, **kwargs):

tacker/vnfm/monitor_drivers/zabbix/zabbix_api.py

@@ -11,7 +11,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 #
-URL_ = "/zabbix/api_jsonrpc.php"
+URL = "/zabbix/api_jsonrpc.php"
 
 HEADERS = {'Content-Type': 'application/json-rpc'}
 dAUTH_API = {'jsonrpc': "2.0",