netdev-dpdk: Fix crash when there is no pci numa info.

netdev-dpdk: Fix crash when there is no pci numa info.

When kernel cannot obtain the pci numa info, the numa_node file
in corresponding pci directory in sysfs will show -1.  Then the
rte_eth_dev_socket_id() function will return it to ovs.  On
current master, ovs assumes rte_eth_dev_socket_id() always
returns non-negative value.  So using this -1 in pmd thread
creation will cause ovs crash.

To fix the above issue, this commit makes ovs always check the
return value of rte_eth_dev_socket_id() and use numa node 0 if
the return value is negative.

Reported-by: Daniel Badea <daniel.badea@windriver.com>
Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Daniele Di Proietto <ddiproietto@vmware.com>