Fix quantum-server startup on SUSE platforms

There was no statment causing openstack-quantum to start during installtion
process.
Remove duplicated service resource for quantum_agent in common_install
Restart quantum-server on SUSE platform immediatley after modyfing /etc/sysconfig/quantum
Set signing_dir in api-paste.ini on SUSE platforms.

Keystone client library by default sets signing_dir to ~/signing_dir. Python
method os.expanduser prefers $HOME over data in /etc/passwd. On SLE11SP3
when server is started by root os.expanduser takes $HOME and expand ~ to /root.