commandserver: switch logging facility to ui.log() interface
The "pager subcommand" message is removed since ui isn't accessible there.
I think that's okay as cmdtable[cmd]() will call attachio() and some debug
message will be printed.
#require serve
$ hg clone http://localhost:$HGPORT/ copy
abort: * (glob)
[255]
$ test -d copy
[1]
$ "$PYTHON" "$TESTDIR/dumbhttp.py" -p $HGPORT --pid dumb.pid
$ cat dumb.pid >> $DAEMON_PIDS
$ hg clone http://localhost:$HGPORT/foo copy2
abort: HTTP Error 404: * (glob)
[255]
$ killdaemons.py