SIGSEGV was caught during tablet streaming, and the reason was
that storage_service::_group0 (via set_group0()) is only set on
shard 0, therefore when streaming ran on any other shard,
it tried to dereference garbage, which resulted in the crash.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closes#15307