tests: add shared mocks and remove bad import

This commit re-adds some of the shared mock fields for testing
and removes a bad import from test_snaplist. These are changes
that shouldn't have been part of the previously reverted patch:
0a70a969d4

subiquity/server/controllers/tests/test_snaplist.py

@@ -14,7 +14,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import unittest
-from unittest.mock import AsyncMock, Mock
+from unittest.mock import AsyncMock
 
 import requests
 

subiquitycore/tests/mocks.py

@@ -43,4 +43,9 @@ def make_app(model=None):
     app.opts = mock.Mock()
     app.opts.dry_run = True
     app.scale_factor = 1000
+    app.echo_syslog_id = None
+    app.log_syslog_id = None
+    app.report_start_event = mock.Mock()
+    app.report_finish_event = mock.Mock()
+
     return app