explicitly convert exit_code to integer

running Windows, spork, minitest throws an error because the exit_code
can't be implicitly converted to integer.  The following error is
thrown:

C:/Ruby193/lib/ruby/gems/1.9.1/gems/spork-minitest-0.0.3/bin/testdrb:7:in
`exit': can't convert DRb::DRbObject into Integer (TypeError)
from
C:/Ruby193/lib/ruby/gems/1.9.1/gems/spork-minitest-0.0.3/bin/testdrb:7:in
`<top (required)>'
from C:/Ruby193/bin/testdrb:23:in `load'
from C:/Ruby193/bin/testdrb:23:in `<main>'