test-obsolete: stabilize output on platforms without 'serve' support

The conditional was updating the repository, which wasn't reflected in
subsequent logs on Windows, so the conditional is narrowed to just the serve
commands.  The serve operation generates log files, so those are deleted to keep
the output of summary consistent.

tests/test-obsolete.t

@@ -719,8 +719,6 b' Template keywords'
   $ hg debugobsolete -r6 -T '{flag} {get(metadata, "user")}\n'
   0 test
 
-#if serve
-
 Test the debug output for exchange
 ----------------------------------
 
@@ -746,6 +744,8 b' check hgweb does not explode'
   $ hg up tip
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
+#if serve
+
   $ hg serve -n test -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
   $ cat hg.pid >> $DAEMON_PIDS
 
@@ -796,6 +796,7 b' reenable for later test'
   $ echo '[experimental]' >> $HGRCPATH
   $ echo "evolution=createmarkers,exchange" >> $HGRCPATH
 
+  $ rm hg.pid access.log errors.log
 #endif
 
 Several troubles on the same changeset (create an unstable and bumped changeset)
@@ -833,7 +834,7 b' test summary output'
   parent: 7:50c51b361e60  (unstable, bumped)
    add babar
   branch: default
-  commit: 3 unknown (clean)
+  commit: (clean)
   update: 2 new changesets (update)
   phases: 4 draft
   unstable: 2 changesets