Strip hyphens from the hostname used in the cert's CN.

CARS doesn't like having hyphens in the hostname, as it breaks their parsing
of the CN.

Change-Id: I6f407687a43e71aa1fb3086609386bb8d26a4337
diff --git a/devcert/gfiber-device-cert b/devcert/gfiber-device-cert
index 10e259a..bc9ca07 100755
--- a/devcert/gfiber-device-cert
+++ b/devcert/gfiber-device-cert
@@ -13,7 +13,8 @@
 host=$(
   hostname -f |
     sed -e 's/\([^.]*\.[^.]*\).*/\1/' \
-        -e 's/\./_/g'
+        -e 's/\./_/g' \
+        -e 's/-//g'
 )
 full_cn="f88fca-Linux-$host"