30ignition: only instmods if module available
30ignition: only instmods if module available

Otherwise we'll error out on kernels which have the functionality
builtin. This was tested on FCOS (which uses `m`) and RHCOS (which uses
`y`). We need to check `/usr/lib/ostree-boot` since on el7 that's the
only place where the config is.

coreos/ignition,coreos/ignition,coreos/ignition