testnode: pass shared_part_list to runTestSuite who understand it

Some test suites who install software during the test, such as SLAPOS-SR
tests, could benefit from reusing already installed shared parts.

The convention is that --shared_part_list is a os.pathsep (:) separated
list of paths of read-only shared parts in which the test is not allowed
to write.

erp5/tests/testERP5TestNode.py

@@ -614,6 +614,7 @@ shared = true
         ('--frontend_url', 'http://frontend/'),
         ('--node_quantity', 3),
         ('--xvfb_bin', part('xserver/bin/Xvfb')),
+        ('--shared_part_list', "/not/exists:/not/exists_either:%s/shared" % node_test_suite.working_directory),
       ):
       parser.add_argument(option[0])
       expected_parameter_list += option

erp5/util/testnode/UnitTestRunner.py

@@ -160,6 +160,11 @@ class UnitTestRunner(object):
         ('--node_quantity', lambda: config['node_quantity']),
         ('--xvfb_bin', lambda: path('xvfb', 'xserver/bin/Xvfb')),
         ('--project_title', lambda: node_test_suite.project_title),
+        ('--shared_part_list', lambda: os.pathsep.join(
+            self._getSlapOSControler(
+                node_test_suite.working_directory,
+                True
+            ).shared_part_list)),
         ):
       if option in supported_parameter_set:
         invocation_list += option, value()