remotefilelog-test: glob some flaky output line

This is similar to ee0959e7d435. The affected line is flaky underload, yet the
final result is correct.  The command involves background pre-check of output,
these are not stable probably because they run in parallel in multiple process.

If it become useful to start testing precise internal details of the, they will
have to be tested in a more appropriate framework than `.t` tests.

Differential Revision: https://phab.mercurial-scm.org/D8179

tests/test-remotefilelog-prefetch.t

@@ -233,9 +233,18 b''
   z2: not copying - file is not managed
   abort: no files to copy
   [255]
+  $ find $CACHEDIR -type f | sort
+.. The following output line about files fetches is globed because it is
+.. flaky, the core the test is checked when checking the cache dir, so
+.. hopefully this flakyness is not hiding any actual bug.
   $ hg revert -a -r 1 || true
-  3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over * (glob)
+  ? files fetched over 1 fetches - (? misses, 0.00% hit ratio) over * (glob)
   abort: z2@109c3a557a73: not found in manifest! (?)
+  $ find $CACHEDIR -type f | sort
+  $TESTTMP/hgcache/master/11/f6ad8ec52a2984abaafd7c3b516503785c2072/ef95c5376f34698742fe34f315fd82136f8f68c0
+  $TESTTMP/hgcache/master/39/5df8f7c51f007019cb30201c49e884b46b92fa/69a1b67522704ec122181c0890bd16e9d3e7516a
+  $TESTTMP/hgcache/master/95/cb0bfd2977c761298d9624e4b4d4c72a39974a/076f5e2225b3ff0400b98c92aa6cdf403ee24cca
+  $TESTTMP/hgcache/repos
 
 # warning when we have excess remotefilelog fetching