when cardtuner is accessed concurrently, there can be a deadlock in code

scenario: 2 threads access cardtune concurrently

MP1-1222-03-07 10:12:45.317892 [(5)]: card: CardTune 3 arte HD Morpheus7:3:-1
MP1-1222-03-07 10:12:45.346894 [(18)]: card: tuned user: epg subchannel: 0
MP1-1222-03-07 10:12:45.374895 [(5)]: card: Tune 3 to arte HD
MP1-1222-03-07 10:12:45.403897 [(18)]: user:epg add

h4. Additional Information
http://forum.team-mediaportal.com/mediaportal-releases-315/tvserver-sometimes-hangs-card-tune-78992/
http://forum.team-mediaportal.com/mediaportal-1-1-0-rc-1-496/tvservice-dying-very-often-78740/index4.html#post589696