EDataBook: Remove unused "handle-cancel-all" signal handler.
EDataBook: Remove unused "handle-cancel-all" signal handler.

EBookClient never invokes this method directly.  Operations are
explicitly cancelled when EBookClient invokes the close() method.

tintou/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server