stop leaking service as a global var

the tls code was leaking out $service as a global variable, which
was causing all manner of confusing errors in grenade trying to
use that variable name. All lower case vars should be localize.

Change-Id: I74fa597f20ee7c714cab83490b42d874ea93db02

lib/tls

@@ -323,7 +323,8 @@ function make_root_CA {
 #
 # Uses global ``SSL_ENABLED_SERVICES``
 function is_ssl_enabled_service {
-    services=$@
+    local services=$@
+    local service=""
     for service in ${services}; do
         [[ ,${SSL_ENABLED_SERVICES}, =~ ,${service}, ]] && return 0
     done