delete, start: remove newline from errors

Error messages should not usually contain newlines.

Testing shows that the error runc delete prints is the same before and
after this commit:

	[kir@kir-rhat runc-tst]$ sudo ../runc/runc delete xx3
	ERRO[0000] cannot delete container xx3 that is not stopped: running
	[kir@kir-rhat runc-tst]$

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

delete.go

@@ -79,7 +79,7 @@ status of "ubuntu01" as "stopped" the following will delete resources held for
 			if force {
 				return killContainer(container)
 			}
-			return fmt.Errorf("cannot delete container %s that is not stopped: %s\n", id, s)
+			return fmt.Errorf("cannot delete container %s that is not stopped: %s", id, s)
 		}
 
 		return nil

start.go

@@ -48,7 +48,7 @@ your host.`,
 		case libcontainer.Running:
 			return errors.New("cannot start an already running container")
 		default:
-			return fmt.Errorf("cannot start a container in the %s state\n", status)
+			return fmt.Errorf("cannot start a container in the %s state", status)
 		}
 	},
 }