Test Digest::HMAC_SHA1 in Zimbra test (#470)

lemonldap-ng-handler/t/51-Lemonldap-NG-Handler-Zimbra.t

@@ -11,5 +11,11 @@ use Test::More tests => 1;
 
 # Insert your test code below, the Test::More module is use()ed here so read
 # its man page ( perldoc Test::More ) for help writing this test script.
-
-use_ok('Lemonldap::NG::Handler::ZimbraPreAuth');
+SKIP: {
+    eval { require Digest::HMAC_SHA1 };
+    skip
+"Digest::HMAC_SHA1 is not installed, so Lemonldap::NG::Handler::ZimbraPreAuth will not be useable",
+      1
+      if ($@);
+    use_ok('Lemonldap::NG::Handler::ZimbraPreAuth');
+}