slapos_pdm: Support Hosting Subscription with many root Software Instances

Since during maintenance of Hosting Subscription it's possible to end up with
many root Software Instances (of which many might be destroy_requested) it's
needed to support such situation while creating upgrade decision and finding
upgradeable Software Release.

master/bt5/slapos_pdm/SkinTemplateItem/portal_skins/slapos_pdm/HostingSubscription_createUpgradeDecision.py

@@ -6,9 +6,12 @@ upgrade_scope = context.getUpgradeScope()
 if upgrade_scope in ["never", "disabled"]:
   return
 
-root_instance = hosting_subscription.getPredecessorValue(portal_type=["Software Instance", "Slave Instance"])
-if root_instance is None:
+root_instance_list = [
+  q for q in hosting_subscription.getPredecessorValueList(portal_type=["Software Instance", "Slave Instance"])
+  if q.getSlapState() != 'destroy_requested']
+if len(root_instance_list) == 0:
   return
+root_instance = root_instance_list[0]
 
 slave_upgrade = False
 if root_instance.getPortalType() == 'Slave Instance':

master/bt5/slapos_pdm/SkinTemplateItem/portal_skins/slapos_pdm/HostingSubscription_getUpgradableSoftwareRelease.py

@@ -11,9 +11,10 @@ slap_state = ['start_requested', 'stop_requested']
 if not hosting_subscription.getSlapState() in slap_state:
   return None
 
-source_instance = hosting_subscription.getPredecessorValue()
-if not source_instance or source_instance.getSlapState() not in slap_state:
+source_instance_list = [q for q in hosting_subscription.getPredecessorValueList() if q.getSlapState() in slap_state]
+if len(source_instance_list) == 0:
   return None
+source_instance = source_instance_list[0]
 
 software_release = hosting_subscription.HostingSubscription_getNewerSofwareRelease()
 if not software_release: