Fix for Column Break if it appears in w:r which is not the first run.

Explicitly ended paragraph when the column break appears in a run
(which is not the first run in the paragraph), as Writer adds a
column break only for new paragraph. Also the created paragraph
must have the same para properties as the earlier one. Hence avoided
pushing new para properties if paragraph is split to adjust a col break.
Added UT for the same.

Conflicts:
	sw/qa/extras/ooxmlexport/ooxmlexport.cxx
Reviewed on:
	https://gerrit.libreoffice.org/6953

Change-Id: If7d503b7a4bfab31f40ceb0119876e5909252b2f