test: enable sparse-revlog for test-revlog-v2.t

We are about to enable sparse-revlog globally. To help with reviewing the
tests change, we isolate them in individual changesets.

Differential Revision: https://phab.mercurial-scm.org/D5333

tests/test-revlog-v2.t

@@ -1,3 +1,9 b''
+TRANSITIONAL CONFIG
+  $ cat << EOF >> $HGRCPATH
+  > [format]
+  > sparse-revlog = yes
+  > EOF
+
 #require reporevlogstore
 
 A repo with unknown revlogv2 requirement string cannot be opened
@@ -24,6 +30,7 b' Can create and open repo with revlog v2 '
   dotencode
   exp-revlogv2.0
   fncache
+  sparserevlog
   store
 
   $ hg log