restore: carefully replace backup config

do not replace the backup policy and other flags

src/settings.js

@@ -24,6 +24,7 @@ exports = module.exports = {
 
     getBackupConfig: getBackupConfig,
     setBackupConfig: setBackupConfig,
+    setBackupCredentials: setBackupCredentials,
 
     getPlatformConfig: getPlatformConfig,
     setPlatformConfig: setPlatformConfig,
@@ -412,6 +413,30 @@ function setBackupConfig(backupConfig, callback) {
     });
 }
 
+function setBackupCredentials(credentials, callback) {
+    assert.strictEqual(typeof credentials, 'object');
+    assert.strictEqual(typeof callback, 'function');
+
+    getBackupConfig(function (error, currentConfig) {
+        if (error) return callback(error);
+
+        // preserve these fields
+        const extra = _.pick(currentConfig, 'retentionSecs', 'intervalSecs', 'copyConcurrency', 'syncConcurrency');
+
+        const backupConfig = _.extend({}, credentials, extra);
+
+        backups.cleanupCacheFilesSync();
+
+        settingsdb.set(exports.BACKUP_CONFIG_KEY, JSON.stringify(backupConfig), function (error) {
+            if (error) return callback(error);
+
+            notifyChange(exports.BACKUP_CONFIG_KEY, backupConfig);
+
+            backups.configureCollectd(backupConfig, callback);
+        });
+    });
+}
+
 function getPlatformConfig(callback) {
     assert.strictEqual(typeof callback, 'function');
 
@@ -458,10 +483,10 @@ function setExternalLdapConfig(externalLdapConfig, callback) {
     assert.strictEqual(typeof externalLdapConfig, 'object');
     assert.strictEqual(typeof callback, 'function');
 
-    getExternalLdapConfig(function (error, curentConfig) {
+    getExternalLdapConfig(function (error, currentConfig) {
         if (error) return callback(error);
 
-        externalLdap.injectPrivateFields(externalLdapConfig, curentConfig);
+        externalLdap.injectPrivateFields(externalLdapConfig, currentConfig);
 
         externalLdap.testConfig(externalLdapConfig, function (error) {
             if (error) return callback(error);