Most of snitch drivers set _my_dc and _my_rack with direct assignment
thus skipping the sanity checks for dc/rack being empty. On other shards
they call set_my_dc_and_rack() helper which warns the empty value and
replaces it with some defaults.
It's better to use the helper on all shards in order to have the same
dc/rack values everywhere.
refs: #12185
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closes#12524
f6e8b64334