tests: add default for opts.kernel_cmdline

Ensure correct behavior in tests when kernel_cmdline is not set
correctly. Also add to the the schema cmd submodules make_app
function so that it doesn't crash when trying to read from
the kernel_cmdline in the ubuntu drivers.

subiquity/cmd/schema.py

@@ -54,6 +54,7 @@ def make_schema(app):
 def make_app():
     parser = make_server_args_parser()
     opts, unknown = parser.parse_known_args(["--dry-run"])
+    opts.kernel_cmdline = {}
     app = SubiquityServer(opts, "")
     # This is needed because the ubuntu-pro server controller accesses dr_cfg
     # in the initializer.

subiquitycore/tests/mocks.py

@@ -45,6 +45,7 @@ def make_app(model=None):
     app.prev_screen = mock.Mock()
     app.hub = MessageHub()
     app.opts = mock.Mock()
+    app.opts.kernel_cmdline = {}
     app.opts.dry_run = True
     app.scale_factor = 1000
     app.echo_syslog_id = None