Incorrect escaping of property names in JcrModifiablePropertyMap on save

This follows SLING-2425 where there was a change in the way JCR properties are escaped before being persited.
The regression happens for properties that have ":" in the name.

For example: jcr:title after the #save() call will turn into jcr%3Atitle so the node will end up with a brand new property, instead of having the old jcr:title updated.