debian: recursively adjust permissions of /var/lib/ceph/crash

debian: recursively adjust permissions of /var/lib/ceph/crash

A rather recent PR made ceph-crash run as "ceph" user instead of
root [0]. However, because /var/lib/ceph/crash/posted belongs to root,
ceph-crash cannot actually post any crash logs now.

This commit fixes this by recursively updating the permissions of
'/var/lib/ceph/crash', which ensures that all files and directories
used by 'ceph-crash.service' are actually owned by the user configured
for Ceph. This also accounts for existing installations.

Additionally, quote interpolated variables and use curly braces [1].

[0]: #48713
[1]: https://www.shellcheck.net/wiki/SC2086

Fixes: https://tracker.ceph.com/issues/64548
Signed-off-by: Max Carrara <m.carrara@proxmox.com>