units: restore sysfs conditions in sys-fs-fuse-connections.mount and sys-kernel-confi...

units: restore sysfs conditions in sys-fs-fuse-connections.mount and sys-kernel-config.mount

Commit 42cc2855ba2fe4c6f5d incorrectly removed the condition on sysfs in both
sys-fs-fuse-connections.mount and sys-kernel-config.mount. However there are
still needed in case modprobe of one of these modules is intentionally skipped
(due to lack of privs for example).

This patch restores the 2 conditions which should be safe for the common case,
since all conditions are only checked after all deps ordered before are
complete.

Follow-up for 42cc2855ba2fe4c6f5dc863507a1c843611350a0.