BUG Fix - cifs file deletion + Reboot will now download like expected

was looking if the VAR was Not Define instead of if the file Not Exist
Restart DNSMASQ instead of Killing it to free memory

Lot of ram got free like before.
But now internet continu to work while the script his running.
AD are not blocked while a new configuration file his generated.
TESTING source url 2

Also tested S10="http://adaway.sufficientlysecure.org/hosts.txt"  #18K -
approx 600 hosts
But this source do not provide "Last Modified" time and cause the script
to always Download/Generate.. it his also quite small so.... rejected