run-tests: use regex when searching for $HGPORT in test output

This prevents spurious errors when a changeset hash happens to match
the port number. Before, this invocation gave a test failure:

  $ ./run-tests.py test-log.t --port 24427
  ERROR: /home/mg/src/mercurial-crew/tests/test-log.t output changed
  --- /home/mg/src/mercurial-crew/tests/test-log.t
  +++ /home/mg/src/mercurial-crew/tests/test-log.t.err
  @@ -626,12 +626,12 @@

     $ hg log -b default
     changeset:   2:c3a4f03cc9a7
  -  parent:      0:24427303d56f
  +  parent:      0:$HGPORT303d56f
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     commit on default

  ...

tests/run-tests.py

@@ -604,7 +604,7 b' def run(cmd, options, replacements):'
             raise
 
     for s, r in replacements:
-        output = output.replace(s, r)
+        output = re.sub(s, r, output)
     return ret, splitnewlines(output)
 
 def runone(options, test, skips, fails):
@@ -677,10 +677,10 b' def runone(options, test, skips, fails):'
         signal.alarm(options.timeout)
 
     ret, out = runner(testpath, options, [
-        (testtmp, '$TESTTMP'),
-        (':%s' % options.port, ':$HGPORT'),
-        (':%s' % (options.port + 1), ':$HGPORT1'),
-        (':%s' % (options.port + 2), ':$HGPORT2'),
+        (re.escape(testtmp), '$TESTTMP'),
+        (r':%s\b' % options.port, ':$HGPORT'),
+        (r':%s\b' % (options.port + 1), ':$HGPORT1'),
+        (r':%s\b' % (options.port + 2), ':$HGPORT2'),
         ])
     vlog("# Ret was:", ret)