cg_build_path: use max FILENAME_MAX characters for array in 2nd parameter
cg_build_path: use max FILENAME_MAX characters for array in 2nd parameter

The function cg_build_path is internal now. All calls of it (there is one
exception - cgroup_fill_cgc function which uses FILENAME_MAX+1, fixed now too)
have the limited second parameter buffer to FILENAME_MAX.

cg_build_path copy to this buffer, but thhere was no limitation of the size of coppied buffer.
This is fixed in the patch.

Signed-off-by: Ivana Hutarova Varekova <2e3918a0a366ea7e658a2062ab582c898a7e1b1b@redhat.com>
Signed-off-by: Jan Safranek <a7f4b96ffdd515ecef00f117294da18555749b0b@redhat.com>

jrfastab/Linux-cgdcbxd,jrfastab/Linux-cgdcbxd,rafalmiel/libcg,jrfastab/Linux-cgdcbxd,rafalmiel/libcg,jrfastab/Linux-cgdcbxd,rafalmiel/libcg,rafalmiel/libcg