local-unbound: Read a tab separated resolv.conf

Use [[:space:]] rather than a white space character to delimit the keys
and the values in the resolv.conf file.

PR:		236079
Reviewed by:	des
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D53811

usr.sbin/unbound/setup/local-unbound-setup.sh

@@ -118,8 +118,8 @@ set_chrootdir() {
 get_nameservers() {
 	while read line ; do
 		local bareline=${line%%\#*}
-		local key=${bareline%% *}
-		local value=${bareline#* }
+		local key=${bareline%%[[:space:]]*}
+		local value=${bareline#*[[:space:]]}
 		case ${key} in
 		nameserver)
 			case ${value} in
@@ -145,8 +145,8 @@ gen_resolv_conf() {
 	local edns0=no
 	while read line ; do
 		local bareline=${line%%\#*}
-		local key=${bareline%% *}
-		local value=${bareline#* }
+		local key=${bareline%%[[:space:]]*}
+		local value=${bareline#*[[:space:]]}
 		case ${key} in
 		nameserver)
 			case ${value} in