[Rakefile] Weathermap creation tool update for working on ruby 1.8.7

Gemfile

@@ -5,7 +5,7 @@ gem 'restfully','1.0.5'
 
 gem "net-admin-common",
   :git => "ssh://g5kadmin@git.grid5000.fr/srv/git/repos/net-admin-common",
-  :tag => "2.2"
+  :tag => "2.3"
 gem "cacti-play",
   :git => "ssh://g5kadmin@git.grid5000.fr/srv/git/repos/cacti-play",
   :tag => "2.4"

Gemfile.lock

@@ -8,10 +8,10 @@ GIT
 
 GIT
   remote: ssh://g5kadmin@git.grid5000.fr/srv/git/repos/net-admin-common
-  revision: a0335cc1d5cb7fcd79b6fc3fb11d5f0bc34bd596
-  tag: 2.2
+  revision: 322b1f8f659edf2a16ab4db1d2728ce8baa3c6fd
+  tag: 2.3
   specs:
-    net-admin-common (2.2)
+    net-admin-common (2.3)
       net-ssh (>= 2.3.0)
       net-ssh-multi (>= 1.1)
       rest-client (>= 1.6.7)