New module: xenserver_guest_facts - returns facts of XenServer VMs (#49426)

* Initial commit for xenserver_guest_facts module
* New module: xenserver_guest_facts. Returns facts of XenServer VMs. Module is fully documented.
* Added unit tests for the module
* Moved FakeXenAPI import to a dedicated fixture, other fixes
* Removed unused imports, minor fixes to unit test code

test/units/modules/cloud/xenserver/FakeXenAPI.py

@@ -0,0 +1,66 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright: (c) 2019, Bojan Vitnik <bvitnik@mainstream.rs>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+FAKE_API_VERSION = "1.1"
+
+
+class Failure(Exception):
+    def __init__(self, details):
+        self.details = details
+
+    def __str__(self):
+        return str(self.details)
+
+
+class Session(object):
+    def __init__(self, uri, transport=None, encoding=None, verbose=0,
+                 allow_none=1, ignore_ssl=False):
+
+        self.transport = transport
+        self._session = None
+        self.last_login_method = None
+        self.last_login_params = None
+        self.API_version = FAKE_API_VERSION
+
+    def _get_api_version(self):
+        return FAKE_API_VERSION
+
+    def _login(self, method, params):
+        self._session = "OpaqueRef:fake-xenapi-session-ref"
+        self.last_login_method = method
+        self.last_login_params = params
+        self.API_version = self._get_api_version()
+
+    def _logout(self):
+        self._session = None
+        self.last_login_method = None
+        self.last_login_params = None
+        self.API_version = FAKE_API_VERSION
+
+    def xenapi_request(self, methodname, params):
+        if methodname.startswith('login'):
+            self._login(methodname, params)
+            return None
+        elif methodname == 'logout' or methodname == 'session.logout':
+            self._logout()
+            return None
+        else:
+            # Should be patched with mocker.patch().
+            return None
+
+    def __getattr__(self, name):
+        if name == 'handle':
+            return self._session
+        elif name == 'xenapi':
+            # Should be patched with mocker.patch().
+            return None
+        elif name.startswith('login') or name.startswith('slave_local'):
+            return lambda *params: self._login(name, params)
+        elif name == 'logout':
+            return self._logout
+
+
+def xapi_local():
+    return Session("http://_var_lib_xcp_xapi/")