Revert "Rely on single private key file for optimized ssh remote fs operations"

This reverts commit aaebe01892.

src/backupsites.js

@@ -51,7 +51,6 @@ const assert = require('node:assert'),
     eventlog = require('./eventlog.js'),
     hush = require('./hush.js'),
     locks = require('./locks.js'),
-    mounts = require('./mounts.js'),
     path = require('node:path'),
     paths = require('./paths.js'),
     safe = require('safetydance'),
@@ -109,12 +108,6 @@ function postProcess(result) {
     result.config = result.configJson ? safe.JSON.parse(result.configJson) : {};
     delete result.configJson;
 
-    // the optimized code paths for rsync remote copy and delete require the keyfile path see filesystem.js:copyInternal()
-    if (result.config._provider === mounts.MOUNT_TYPE_SSHFS) {
-        const privateKeyFilePath = path.join(paths.SSHFS_KEYS_DIR, `identity_file_${result.id}`);
-        result.config.mountOptions = { ...result.config.mountOptions, _privateKeyFile: privateKeyFilePath };
-    }
-
     result.limits = safe.JSON.parse(result.limitsJson) || {};
     delete result.limitsJson;