...to fix the import part of tdf#86087.  Apparently, "fragment-only" relative
same-document URLs (like <#anchor>) are supposed to remain relative; otherwise,
various tests like testFdo69548::Import in CppunitTest_sw_ooxmlimport fail.

Change-Id: I2dbba2f2f1e225f85e21600e68a3c4cffdb023b2