Fix Octavia health manager

Recently, there is a change[1] in Octavia which adding new validation
to forbid using HTTP method, expectation code and URL path for non-HTTP
type health monitor. For example, if user is using TCP as the type of
health monitor and now Heat is using default values for HTTP_METHOD,
EXPECTED_CODES and URL_PATH, which will cause error response from Octavia.
And the stack creation will fail. This patch fixes it by removing those
default values.

[1] e1e1640af5

Task: 22876
Story: 2002904

Change-Id: Id61cde4c1416cc65b4eac90710f564699ada6a75

heat/engine/resources/openstack/octavia/health_monitor.py

@@ -69,14 +69,12 @@ class HealthMonitor(octavia_base.OctaviaBase):
               'values: a single value, such as 200. a list, such as 200, 202. '
               'a range, such as 200-204.'),
             update_allowed=True,
-            default='200'
         ),
         HTTP_METHOD: properties.Schema(
             properties.Schema.STRING,
             _('The HTTP method used for requests by the monitor of type '
               'HTTP.'),
             update_allowed=True,
-            default=GET,
             constraints=[constraints.AllowedValues(HTTP_METHODS)]
         ),
         MAX_RETRIES: properties.Schema(
@@ -117,7 +115,6 @@ class HealthMonitor(octavia_base.OctaviaBase):
               'test a member health. A valid value is a string the begins '
               'with a forward slash (/).'),
             update_allowed=True,
-            default='/'
         ),
         TENANT_ID: properties.Schema(
             properties.Schema.STRING,