ssa_db_helper.c: adding better dump directory handling

The following cases are handled:
- In case of non-existent directory for dump it will
  be created.
- In case of non-empty directory it will be cleared.

Signed-off-by: Ilya Nelkenbaum <ilyan@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>