ssa.c: In ssa_downstream_handle_query_data, set connection phase back to IDLE

when last data table transferred

This allows subsequent (PR)DB queries to work rather than the following
being detected and logged on upstream side:
ssa_downstream_handle_query_defs: WARNING - rsock 53 phase 4 not SSA_DB_IDLE for SSA_MSG_DB_QUERY_DEF

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