mon: OSDMonitor: fix a bug introduced on 97462a32

Fixes: #5737
Backport: cuttlefish

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
test: test_store_tool: global init before using LevelDBStore

Fixes a segfault

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>