add python-omniorb-omg to python-omniorb

python-omniorb-omg is recommended package of python-omniorb and it is not installed jenkins.ros.org (http://jenkins.ros.org/job/devel-hydro-hrpsys/ARCH_PARAM=amd64,UBUNTU_PARAM=precise,label=devel/46/consoleFull)

```
Package: python-omniorb                  
State: installed
Automatically installed: yes
Version: 3.6-1
Priority: optional
Section: universe/python
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Architecture: amd64
Uncompressed Size: 2,828 k
Depends: python2.7, python (>= 2.7.1-0ubuntu2), python (< 2.8), libc6 (>= 2.4), libgcc1
         (>= 1:4.1.1), libomniorb4-1 (>= 4.1.5), libomnithread3c2 (>= 4.0.6),
         libstdc++6 (>= 4.1.1)
Recommends: python-omniorb-omg
Conflicts: python-omniorb

```