BUG-1382: do not instantiate prefixed QNames

Prefix-aware QName constructor is going away, do not use it. Also fix
all references to QName.getPrefix().

Change-Id: Ife6567a269c2db16019ae97a6eace74a19ac3b23
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-1382: do not instantiate prefixed QNames"