dw-start.sh minor tweaks

[guitarpicva]

On line 45 suggest changing the default DIREWOLF variable to the much more common value of "/usr/local/bin/direwolf"

THEN....

On line 175 suggest changing the literal "grep direwolf" to grep "$DWCMD"

In my case, my RPi is named direwolf2 (direwolf on an RPi2). Thus I have many lines in "ps ax" which report true to a grep direwolf

I have made these adjustments and it seems to be functioning as designed. It may help others as well, and particularly those with default installations. It's still not bullet-proof but it's a bit better for the general use case.