Branch:b1_6

Branch:b1_6
b:11662
compare fed_grant and client current grant, and decide whether we should grant
more space to client or keep the original fed_grant and return the client fed_grant,
instead of that "new granted" space, because client will call osc_init_grant instead of
osc_update_grant to reset the grant info of client.
i:adilger, green