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

This pull request adds both of these to the packaging.