Update env.go

Sirupsen/logrus needs to be renamed to sirupsen/logrus
https://github.com/vmware/vsphere-storage-for-docker/issues/2000

env.go

 	"strconv"
 	"strings"
 
-	log "github.com/Sirupsen/logrus"
+	log "github.com/sirupsen/logrus"
 	"github.com/goanywhere/fs"
 )