Make a deep copy of extra_args before modifying it in set_dash_test_params (#3270)
Make a deep copy of extra_args before modifying it in set_dash_test_params (#3270)

Otherwise we end up having the same list instance for every entry in
extra_args, which means modifying index 0 also affects all other indexes.

Noticed this while looking at "ps aux | grep dashd" output. It turned out
that parameters like "-dip3params" were passed multiple times to each node.
UdjinM6/dash,dashpay/dash,dashpay/dash,thelazier/dash,dashpay/dash,dashpay/dash,UdjinM6/dash,dashpay/dash,thelazier/dash,UdjinM6/dash,UdjinM6/dash,thelazier/dash,UdjinM6/dash,thelazier/dash,thelazier/dash