PluginManager: Do not use instance() when that is not needed

Change-Id: I68e1b20561098c375557be6db1fb528e0ae040f6
Reviewed-by: hjk <hjk121@nokiamail.com>
VCS: Use outputCodec for stdErr

Change-Id: I0e9b4b1aa48bfab8ff84d2559d6971ca9fdde5b6
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>