letsencrypt.sh hook script: work with TOKEN_VALUE starting with -.

argparse refuses to accept `--option -foo` but reliably accepts
`--option=-foo` syntax (https://bugs.python.org/issue9334).

Also fixed $@ -> "$@".  Probably makes no difference
(don't think args provided by letsencrypt can contain spaces)
but the only reason to use $@ over $* is its 1:1 expansion in "$@"...

examples/letsencrypt.default.sh

@@ -13,7 +13,7 @@ function deploy_challenge {
 
     echo "deploy_challenge called: ${DOMAIN}, ${TOKEN_FILENAME}, ${TOKEN_VALUE}"
 
-    lexicon $PROVIDER create ${DOMAIN} TXT --name "_acme-challenge.${DOMAIN}." --content "${TOKEN_VALUE}"
+    lexicon $PROVIDER create ${DOMAIN} TXT --name="_acme-challenge.${DOMAIN}." --content="${TOKEN_VALUE}"
 
     sleep 30
 
@@ -40,7 +40,7 @@ function clean_challenge {
 
     echo "clean_challenge called: ${DOMAIN}, ${TOKEN_FILENAME}, ${TOKEN_VALUE}"
 
-    lexicon $PROVIDER delete ${DOMAIN} TXT --name "_acme-challenge.${DOMAIN}." --content "${TOKEN_VALUE}"
+    lexicon $PROVIDER delete ${DOMAIN} TXT --name="_acme-challenge.${DOMAIN}." --content="${TOKEN_VALUE}"
 
     # This hook is called after attempting to validate each domain,
     # whether or not validation was successful. Here you can delete
@@ -94,4 +94,4 @@ function unchanged_cert {
     #   The path of the file containing the intermediate certificate(s).
 }
 
-HANDLER=$1; shift; $HANDLER $@
+HANDLER=$1; shift; $HANDLER "$@"