Fixed missing hyperlink end tag

Problem Description :
The <w:hyperlink> tag is not terminated properly due to that the file get corrupted.
Also unit test is added for export.

Conflicts:
	sw/qa/extras/ooxmlexport/ooxmlexport.cxx
Revewied on:
	https://gerrit.libreoffice.org/6619

Change-Id: I2480ab624ab572e411bd1511030c0da1b7f5d183