Fix RemoveSpace memory leak.
Fix RemoveSpace memory leak.

RemoveSpace now deletes the input space. This fixes a memory leak
related to background compaction.

Change-Id: I7123297adb475b1045f7d1a42d595c53daad0faa

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst