cephadm: avoid double counting NVMe devices in host facts

cephadm: avoid double counting NVMe devices in host facts

- On some systems,the same NVMe drive appears twice in /sys/block,once as the real device
(ex: nvme2n1) and once as a sysfs only alias (ex: nvme2c2n1).
- To avoid counting the same disk twice, we filter /sys/block and only consider entries that have a
valid 'dev' attribute and a corresponding '/dev' node.

Fixes: https://tracker.ceph.com/issues/75342
Signed-off-by: Ujjawal Anand <ujjawal.anand@ibm.com>