test: use bundle2 for exchange in test-largefile

Using bundle2 for exchange unlock the usage of changegroup version 2. This
version of the changegroup held more information (delta base) that result in a
small increase in content size.

It also lead to reordering of output because the exchange scheduling is a bit
different.

tests/test-largefiles.t

@@ -19,6 +19,10 b' It contains all the testing of the basic'
   > usercache=${USERCACHE}
   > [hooks]
   > precommit=sh -c "echo \\"Invoking status precommit hook\\"; hg status"
+  > [experimental]
+  > # drop me once bundle2 is the default,
+  > # added to get test change early.
+  > bundle2-exp = True
   > EOF
 
 Create the repo with a couple of revisions of both large and normal
@@ -1098,18 +1102,18 b' redo pull with --lfrev and check it pull'
   searching for changes
   all local heads known remotely
   6 changesets found
+  uncompressed size of bundle content:
+      1333 (changelog)
+      1599 (manifests)
+       254  .hglf/large1
+       564  .hglf/large3
+       572  .hglf/sub/large4
+       182  .hglf/sub2/large6
+       182  .hglf/sub2/large7
+       212  normal1
+       457  normal3
+       465  sub/normal4
   adding changesets
-  uncompressed size of bundle content:
-      1213 (changelog)
-      1479 (manifests)
-       234  .hglf/large1
-       504  .hglf/large3
-       512  .hglf/sub/large4
-       162  .hglf/sub2/large6
-       162  .hglf/sub2/large7
-       192  normal1
-       397  normal3
-       405  sub/normal4
   adding manifests
   adding file changes
   added 6 changesets with 16 changes to 8 files