rds: IB: fix returned value not set error

rds: IB: fix returned value not set error

When IB port link up/down too frequently, the following will occur.
"
16:57:08  kernel: mlx5_core 0000:af:00.1 enp175s0f1: Link up
16:57:08  kernel: RDS/IB: PORT-EVENT: port active, PORT:
          mlx5_0/port_2/enp175s0f1 : port state transition to UP
          (portlayers 0x7)
16:57:08  kernel: RDS/IB: NET-EVENT: NETDEV-CHANGE, PORT
          mlx5_0/port_2/enp175s0f1 : port state transition NONE -
          port retained in state UP (portlayers 0x7)
16:57:13  kernel: mlx5_core 0000:af:00.1 enp175s0f1: Link down
16:57:13  kernel: RDS/IB: PORT-EVENT: port error, PORT:
          mlx5_0/port_2/enp175s0f1 : port state transition to DOWN
          (portlayers 0x4)
16:57:13  kernel: RDS/IB: NET-EVENT: NETDEV-CHANGE, PORT
          mlx5_0/port_2/enp175s0f1 : port state transition NONE -
          port retained in state DOWN (portlayers 0x4)
16:57:13  kernel: RDS/IB: Address already exist
16:57:17  kernel: mlx5_core 0000:af:00.1 enp175s0f1: Link up
16:57:17  kernel: RDS/IB: PORT-EVENT: port active, PORT:
          mlx5_0/port_2/enp175s0f1 : port state transition to UP
          (portlayers 0x7)
16:57:17  kernel: RDS/IB: NET-EVENT: NETDEV-CHANGE, PORT
          mlx5_0/port_2/enp175s0f1 : port state transition NONE -
          port retained in state UP (portlayers 0x7)
16:57:18  kernel: RDS/IB: IPv4 172.16.2.52 migrated from enp175s0f0
          (port 1) to enp175s0f1 (port 2)
"
From the above, rds_ib_addr_exist is called to check ip address. If
exists, the function goes to the end directly while the ret is not set.
This is not reasonable. This will make some global variables error.

Orabug: 28356474

Signed-off-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Reviewed-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>