Add multipath support to SF

The original SolidFire plugin didn't require/use multipath.  Other
products in the NDVP however require it and we've had a number of
cases where customers have setup multipath with then in turn breaks
the ability to use SF unless the SF device is blacklisted in the
multipath.conf file.

Rather than have two configs, just add multipath support to SF.

Closes Github Issue: NetApp#49

storage_drivers/solidfire_san.go

@@ -431,6 +431,18 @@ func (d *SolidfireSANStorageDriver) Attach(name, mountpoint string, opts map[str
 		return errors.New("iSCSI attach error")
 	}
 	log.Debugf("Attached volume at (path, devfile): %s, %s", path, device)
+
+	// NOTE(jdg): Check for device including multipath/DM device)
+	info, err := utils.GetDeviceInfoForLuns()
+	for _, e := range info {
+        if e.Device != device {
+            continue
+        }
+        if e.MultipathDevice != "" {
+            device = e.MultipathDevice
+        }
+	}
+
 	if utils.GetFSType(device) == "" {
 		//TODO(jdg): Enable selection of *other* fs types
 		err := utils.FormatVolume(device, "ext4")