net/virtio-user: fix string overflow

net/virtio-user: fix string overflow

When parsing /proc/self/maps to get hugepage information, the string
was being copied with strcpy(), which could, theoretically but in fact
not possiblly, overflow the destination buffer. Anyway, to avoid the
false alarm, we replaced strncpy with snprintf for safely copying the
strings.

Coverity issue: 127484
Fixes: 6a84c37e3975 ("net/virtio-user: add vhost-user adapter layer")

Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>