Handle scheduler default filters as sequence

In order to add just additional filters on cluster level
instead of copy/paste all existing list plus additional ones.
Both string and sequence are supported since Queens version.

Change-Id: I55b5a045b4615e12788a358f25f47698d70653aa
diff --git a/README.rst b/README.rst
index 98806c0..220b8eb 100644
--- a/README.rst
+++ b/README.rst
@@ -601,6 +601,14 @@
       # Then add your custom filter on the end (make sure to include all other ones that you need as well)
       scheduler_default_filters: "DifferentHostFilter,SameHostFilter,RetryFilter,AvailabilityZoneFilter,RamFilter,CoreFilter,DiskFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter,PciPassthroughFilter,MyCustomFilter"
 
+      # Since Queens version a sequence could be used as well:
+      ~scheduler_default_filters:
+         - DifferentHostFilter
+         - SameHostFilter
+           ...
+         - MyCustomFilter
+
+
 Hardware Trip/Unmap Support
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