ECalBackendHttp: Ignore cancellations when retrieving data.
ECalBackendHttp: Ignore cancellations when retrieving data.

Helps avoid emitting uninteresting error messages to clients.

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