app/testpmd: fix DCB forwarding configuration

app/testpmd: fix DCB forwarding configuration

After DCB mode is configured, the operations of port stop and port start
change the value of the global variable "dcb_test", As a result, the
forwarding configuration from DCB to RSS mode, namely,
“dcb_fwd_config_setup()” to "rss_fwd_config_setup()".

Currently, the 'dcb_flag' field in struct 'rte_port' indicates whether
the port is configured with DCB. And it is sufficient to have
'dcb_config' as a global variable to control the DCB test status. So
this patch deletes the "dcb_test".

In addition, setting 'dcb_config' at the end of init_port_dcb_config()
in case that ports fail to enter DCB mode.

Fixes: 900550de04a7 ("app/testpmd: add dcb support")
Fixes: ce8d561418d4 ("app/testpmd: add port configuration settings")
Fixes: 7741e4cf16c0 ("app/testpmd: VMDq and DCB updates")
Cc: stable@dpdk.org
Signed-off-by: Huisong Li <lihuisong@huawei.com>
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Acked-by: Xiaoyun Li <xiaoyun.li@intel.com>