client: Pass --delete to rsync

[apostergiou]

With this change, we delete extraneous files from the destination dir.

The produced command is:

rsync --delete -rtlp apostergiou@localhost::mistry/simple/ready/c8d654f58623063cb55e0790890ad5aada1235be093ced09f7057e366b2de264/data/artifacts/* /tmp/foo

# client request

$ ./mistry-cli build --host localhost --port 8462 --project simple --group $RANDOM --target /tmp/foo --transport rsync -- --flavor=$RANDOM --x=$RANDOM

[agis]

This is not urgent, so I think we should solve it just by making the client transport flags configurable.

[apostergiou]

This is not urgent, so I think we should solve it just by making the client transport flags configurable.

True, I opened an issue to track it #35, so we can close this pull request.