Fixed escape sequence in wiki module

wiki/manifests/init.pp

@@ -99,7 +99,7 @@ class wiki::collab::base {
             exec { "usermod-www-data":
                 path    => "/bin:/usr/bin:/sbin:/usr/sbin",
                 command => "usermod -a -G collab www-data",
-                unless  => "id -n -G www-data | grep '\bcollab\b'",
+                unless  => "id -n -G www-data | grep '\\bcollab\\b'",
             }
         }
     }