[WIP] Hotfix for the `serverspec`'s bahaviour change.

Serverspec offers the information about the target server,
providing `os` hashes.

Noticed that `os[:release]` does not return release names,
such as "precise", but rather "12.04".

Due to this behavioural change, tests breaks.
Change the condition to follow the `serverspec`'s behavioural change.

Serverspec offers the information about the target server,
providing `os` hashes.

Noticed that `os[:release]` no longer returns the release names,
such as "precise", but rather "12.04".

Due to this behavioural change, tests breaks.

This commit is intended to fix this problem:

```
diff --git a/site-cookbooks/base/test/integration/default/serverspec/packages_spec.rb b/site-cookbooks/base/test/integration/default/serverspec/packages_spec.rb
index 38895bf..1b8ce0f 100644
--- a/site-cookbooks/base/test/integration/default/serverspec/packages_spec.rb
+++ b/site-cookbooks/base/test/integration/default/serverspec/packages_spec.rb
@@ -24,7 +24,7 @@ describe package('ruby') do
   it { should be_installed }
 end

-if os[:release].include?("precise")
+if os[:release] == "12.04"
   describe package('rubygems') do
     it { should be_installed }
   end
```
Merge pull request #143 from kazu634/hotfix-for-base-test

Hotfix for the `serverspec`'s bahaviour change.