If only one interface available, don't show whiptail, just use that interface.

Signed-off-by: Dan Schaper <dan.schaper@pi-hole.net>

automated install/basic-install.sh

@@ -247,6 +247,11 @@ chooseInterface() {
   # Loop sentinel variable
   local firstLoop=1
 
+  if [[ $(echo ${availableInterfaces} | wc -l) -eq 1 ]]; then
+      PIHOLE_INTERFACE=${availableInterfaces}
+      return
+  fi
+
   while read -r line; do
     mode="OFF"
     if [[ ${firstLoop} -eq 1 ]]; then