Fix hopefully last reference in test_template_constant_dict to account for addition of sysroot template

Author: Caspar van Leeuwen

test/framework/easyconfig.py

@@ -3409,6 +3409,7 @@ def test_template_constant_dict(self):
             'namelower': 'foo',
             'nameletter': 'f',
             'nameletterlower': 'f',
+            'sysroot': '',
             'version': '1.2.3',
             'version_major': '1',
             'version_major_minor': '1.2',