ExtCfRuleContext::onStartElement processing depends on some data now buffered
until CondFormatBuffer::finalizeImport runs. We now need to wait for this
data to be available. This change buffers up the processing that used happen
in ExtCfRuleContext startElement so it is now done as part of
CondFormatBuffer::finalizeImport

Change-Id: Ifbfe12740e6c4bc9791183dba89acb79cbbb6ef6