Fix logging in Listener.cpp
Fix logging in Listener.cpp

Clear() log message was claiming it was the destructor, which had me very confused when looking
at the log messages. Fix the message, and add a log message to the real destructor.

Also noticed that the destructor was needlessly locking the broadcaster mutex (as Clear was
locking it again anyway), so remove that as well.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@269058 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb