Add API setProhibitMode in HdmiControlService

setProhibitMode sets a flag inside the service that indicates if
input switch request will be processed or not. Sets to true when
TV is doing something for which TV display should be fixed, like
channel scan, software update - collectively called 'prohibit mode'.

Change-Id: I8ac623023210b58b684b9af3ac475a5fe0d09435