packaging: add missing test files

Two tests were inadvertantly missing from the RPM packaging:

ceph_test_c_headers was added to ceph in
ffdd30efc870eafb1047f022b16d9680d88fcc78

ceph_test_get_blkdev_size was added to ceph in
324dd54534e41598feb6169f33cfed85495fa91f

Add both of these to the packaging.

Signed-off-by: Ken Dreyer <ken.dreyer@inktank.com>
Merge pull request #1093 from kdreyer-inktank/redhat-missing-tests

packaging: add missing test files

Reviewed-by: Sage Weil <sage@inktank.com>