bug #3315: use semantic versioning for remotes

onehost sync was using alphabetical comparison but this method does not work for this
comparison:

4.10.0 > 4.8.0

Now the versions are parsed by Gem::Version, that comes with rubygems and should
be installed in the frontend.

When the version can not be parsed it falls back to text comparison or forces update
if the comparison can not be made (one of the two versions is malformed).

More information about semantic versioning: http://semver.org/

src/cli/one_helper/onehost_helper.rb

@@ -16,6 +16,7 @@
 
 require 'one_helper'
 require 'one_helper/onevm_helper'
+require 'rubygems'
 
 class OneHostHelper < OpenNebulaHelper::OneHelper
     TEMPLATE_XPATH  = '//HOST/TEMPLATE'
@@ -178,6 +179,12 @@ class OneHostHelper < OpenNebulaHelper::OneHelper
             exit(-1)
         end
 
+        begin
+            current_version = Gem::Version.new(current_version)
+        rescue
+            STDERR.puts "VERSION file is malformed, use semantic versioning."
+        end
+
         cluster_id = options[:cluster]
 
         # Get remote_dir (implies oneadmin group)
@@ -218,8 +225,17 @@ class OneHostHelper < OpenNebulaHelper::OneHelper
 
             host_version=host['TEMPLATE/VERSION']
 
+            begin
+                host_version = Gem::Version.new(host_version)
+            rescue
+            end
+
             if !options[:force]
-                next if host_version && host_version >= current_version
+                begin
+                    next if host_version && host_version >= current_version
+                rescue
+                    STDERR.puts "Error comparing versions for host #{host['NAME']}."
+                end
             end
 
             puts "* Adding #{host['NAME']} to upgrade"