locale: Add in the default locale for Mendel

Change-Id: I584b17c6fbb76983d0dd9c81c5e38cc94b384822
diff --git a/debian/postinst b/debian/postinst
index d8a7884..2df2b1a 100755
--- a/debian/postinst
+++ b/debian/postinst
@@ -14,6 +14,7 @@
 # Choose a locale and regenerate it to eliminate LC warnings.
 echo en_US.UTF-8 UTF-8 >/etc/locale.gen
 locale-gen
+echo LANG=en_US.UTF-8 >/etc/locale.conf
 
 # Add the aiy user and give them all the access they need.
 adduser aiy --home /home/aiy --shell /bin/bash --disabled-password --gecos "" || true