fix ganglia::gmetad::{install,config} ordering issue

`ganglia::gmetad` would fail on el6.x when the /etc/ganglia dir wasn't present
as it was trying to create the configuration file before the RPM was installed
(which may create that dir).  This wasn't seen in my test env as ganglia::gmond
/ the gmond RPM were always creating that dir.  Turned up by the rspec-system
tests.

manifests/gmetad.pp

@@ -53,8 +53,8 @@
   validate_string($gridname)
 
   anchor{ 'ganglia::gmetad::begin': } ->
-  class{ 'ganglia::gmetad::config': } ->
   class{ 'ganglia::gmetad::install': } ->
+  class{ 'ganglia::gmetad::config': } ->
   class{ 'ganglia::gmetad::service': } ->
   anchor{ 'ganglia::gmetad::end': }
 }