wcfs: Fix fusermount for NEO storage \w > 1 master

We use the zuri for the FsName. The NEO uri contains commas if the
respective cluster uses more than one master node [1]. Unfortunately
fusermount doesn't support commas in mount options, because mount
options are separated from each other by commas [2], [3]. Therefore before
this patch WCFS failed to mount the filesystem if the NEO cluster had
more than one master: this failure is fixed now.

[1] https://lab.nexedi.com/kirr/neo/blob/8c974485/go/neo/client.go#L613
[2] https://www.man7.org/linux/man-pages/man1/fusermount3.1.html
[3] https://lab.nexedi.com/kirr/go-fuse/blob/4a0e6eb5/fuse/server.go#L186

wcfs/wcfs.go

@@ -2466,7 +2466,14 @@ func _main() (err error) {
 	}
 
 	opts := &fuse.MountOptions{
-		FsName: zurl,
+		// Replace prohibited commas with semicolon (they are used
+		// for separating our masters from each other).
+		// Unfortunately fusermount uses commas to separate mountoptions
+		// from each other [1]. Escaping FsName with either " or ' or \"
+		// doesn't help, so lets simply replace all commas with ";".
+		//
+		// [1] https://www.man7.org/linux/man-pages/man1/fusermount3.1.html
+		FsName: strings.Replace(zurl, ",", ";", -1),
 		Name:   "wcfs",
 
 		// We retrieve kernel cache in ZBlk.blksize chunks, which are 2MB in size.

[Levin Zimmermann]

TODO: I should check if this is also necessary somewhere else (maybe in wcfs/__init__.py?) and if this is really the ideal place for this patch.