placesManager.js: Add mounts with no associated volume. (#13325)

This reverts part of af72ce0. While it likely doesn't affect
anything in core Cinnamon (changing what isRemovable() checks
would probably keep these mounts hidden anyhow), other applets
might choose to display these.

See linuxmint/nemo#3670.

Ref:
linuxmint/mint22.3-beta#67.

Author: mtwebster

js/ui/placesManager.js

@@ -465,6 +465,15 @@ PlacesManager.prototype = {
             }
         }
 
+        /* add mounts that have no volume (/etc/mtab mounts, ftp, sftp,...) */
+        let mounts = this._volumeMonitor.get_mounts();
+        for(let i = 0; i < mounts.length; i++) {
+            if(mounts[i].get_volume())
+                continue;
+
+            this._addMount(mounts[i]);
+        }
+
         /* We emit two signals, one for a generic 'all places' update
          * and the other for one specific to mounts. We do this because
          * clients like PlaceDisplay may only care about places in general