Relax and fix constraint.

connection_xml was not correctly validated.
connection_xml and sla_xml are optional, so their dict can evaluate to None or {},
which is False.

master/bt5/vifib_base/PropertySheetTemplateItem/portal_property_sheets/SoftwareInstanceConstraint/connection_xml_valid_xml_constraint.xml

@@ -26,7 +26,7 @@
         </item>
         <item>
             <key> <string>expression</string> </key>
-            <value> <string>python: context.getConnectionXml()</string> </value>
+            <value> <string>python: context.getConnectionXmlAsDict() or True</string> </value>
         </item>
         <item>
             <key> <string>id</string> </key>

master/bt5/vifib_base/PropertySheetTemplateItem/portal_property_sheets/SoftwareInstanceConstraint/sla_xml_valid_xml_constraint.xml

@@ -26,7 +26,7 @@
         </item>
         <item>
             <key> <string>expression</string> </key>
-            <value> <string>python: context.getSlaXmlAsDict()</string> </value>
+            <value> <string>python: context.getSlaXmlAsDict() or True</string> </value>
         </item>
         <item>
             <key> <string>id</string> </key>

master/bt5/vifib_base/bt/revision

-408
\ No newline at end of file
+409
\ No newline at end of file