Fix-up r254141: in the process of making a failing vm_page_rename()
a call of pager_swap_freespace() was moved around, now leading to freeing
the incorrect page because of the pindex changes after vm_page_rename().

Get back to use the correct pindex when destroying the swap space.

Sponsored by:	EMC / Isilon storage division
Reported by:	avg
Tested by:	pho
MFC after:	7 days