shell: exec encoding is utf8 by default and no shell

explicitly mark calls that require the shell

src/sftp.js

@@ -123,8 +123,8 @@ async function start(existingInfra) {
                 ${readOnly} -v /tmp -v /run "${image}" ${cmd}`;
 
     // ignore error if container not found (and fail later) so that this code works across restarts
-    await shell.promises.exec('stopSftp', 'docker stop sftp || true', {});
-    await shell.promises.exec('removeSftp', 'docker rm -f sftp || true', {});
+    await safe(shell.promises.exec('stopSftp', 'docker stop sftp', {})); // ignore error
+    await safe(shell.promises.exec('removeSftp', 'docker rm -f sftp', {})); // ignore error
     await shell.promises.exec('startSftp', runCmd, {});
 }