tests: allow age to go up to triple digits in test-shelve.t

We started to glob the age of shelved changes in 51934fc796c0, which says that
sometimes tests run slow and `hg shelve --list` says "2s" instead of "1s".
However in some instances, like [1], tests run so slow that the age goes up to
double digits ("13s" in that case). When that happens, `hg shelve --list`
output has less white spaces after the age, so let's glob the spaces too. We
probably won't ever need to handle triple digits there, but I went ahead and
left only 2 required white spaces in total.

[1]: https://buildd.debian.org/status/fetch.php?pkg=mercurial&arch=sparc64&ver=4.5-1&stamp=1518360804&raw=0

tests/test-shelve.t

@@ -1711,7 +1711,7 Unshelve respects --keep even if user in
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo 3 >> file && hg ci -Am 13
   $ hg shelve --list
-  default         (*s ago)    changes to: 1 (glob)
+  default         (*s ago) * changes to: 1 (glob)
   $ hg unshelve --keep
   unshelving change 'default'
   rebasing shelved changes
@@ -1727,7 +1727,7 Unshelve respects --keep even if user in
   rebasing 2:3fbe6fbb0bef "changes to: 1" (tip)
   unshelve of 'default' complete
   $ hg shelve --list
-  default         (*s ago)    changes to: 1 (glob)
+  default         (*s ago) * changes to: 1 (glob)
   $ cd ..
 
 Unshelving when there are deleted files does not crash (issue4176)