Cleanup some requirements of spec file

Merge some changes from the current ceph.spec file of the opensuse build service (where we currently build for the following RPM based distros: RHEL/CentOS6, Fedora 16-18, openSUSE 11.4-12.3/Factory and SLE11SP2 (all on x86 and x86_64)) back to git.

Should also fix tcc#4027