init-ifupdown: fix script when '/etc/resolv.conf' is a file

The readlink command on a real file was expanding to nothing and then
the '/etc/resolv.conf' file was not being updated with the nameservers.
With this change we only run the 'readlink' link command after checking
that the file is actually a symbolic link.

Signed-off-by: Javier Viguera <javier.viguera@digi.com>

meta-digi-dey/recipes-core/init-ifupdown/init-ifupdown-1.0/resolv

@@ -18,7 +18,10 @@
 # Only for static method
 [ "${METHOD}" != "static" ] && exit 0
 
-RESOLVCONF="$(readlink /etc/resolv.conf)"
+RESOLVCONF="/etc/resolv.conf"
+
+# For symlinks reset to the destination file
+[ -h "${RESOLVCONF}" ] && RESOLVCONF="$(readlink ${RESOLVCONF})"
 
 NAMESERVERS=""
 for NS in ${IF_DNS_NAMESERVER} ${IF_DNS_NAMESERVERS}; do