libmachine/drivers/rpc: close plugin binary even when driver server fails
libmachine/drivers/rpc: close plugin binary even when driver server fails

With this commit the RPC client driver tries closing the plugin binary
even when closing the driver server fails. This prevents the driver
process from entering in <defunct> state when it failed before closing.

Signed-off-by: André Carvalho <cfe6901433036929a89ffc229c7040a9bd48955e@gmail.com>

dweomer/docker-machine,Herbis/machine,flavio/machine,voutilad/machine,ibuildthecloud/machine,larsla/machine,dweomer/docker-machine,docker/machine,SvenDowideit/machine,ibuildthecloud/machine,Herbis/machine,dgageot/machine,larsla/machine,flavio/machine,londoncalling/machine,exoscale/docker-machine,voutilad/machine,SvenDowideit/machine,exoscale/docker-machine,londoncalling/machine,docker/machine,dgageot/machine