maintainers: add maintainer for replay* files

Updating MAINTAINERS to set Pavel Dovgalyuk as record/replay maintainer
and Paolo Bonzini as a reviewer.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-id: 20170503113304.8704.13997.stgit@PASHA-ISP
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
