fstest: fix parsing of commas in -remotes

Connection string remotes like "TestGoogleCloudStorage,directory_markers:" use
commas. Before this change, these could not be passed with the -remotes flag,
which expected commas to be used only as separators.

After this change, CSV parsing is used so that commas will be properly
recognized inside a terminal-escaped and quoted value, like:

-remotes local,\"TestGoogleCloudStorage,directory_markers:\"

fstest/test_all/test_all.go

@@ -11,6 +11,7 @@ Make TesTrun have a []string of flags to try - that then makes it generic
 */
 
 import (
+	"encoding/csv"
 	"flag"
 	"fmt"
 	"math/rand"
@@ -79,7 +80,14 @@ func main() {
 
 	// Filter selection
 	if *testRemotes != "" {
-		conf.filterBackendsByRemotes(strings.Split(*testRemotes, ","))
+		// CSV parse to support connection string remotes with commas like -remotes local,\"TestGoogleCloudStorage,directory_markers:\"
+		r := csv.NewReader(strings.NewReader(*testRemotes))
+		remotes, err := r.Read()
+		if err != nil {
+			fs.Fatalf(*testRemotes, "error CSV-parsing -remotes string: %v", err)
+		}
+		fs.Debugf(*testRemotes, "using remotes: %v", remotes)
+		conf.filterBackendsByRemotes(remotes)
 	}
 	if *testBackends != "" {
 		conf.filterBackendsByBackends(strings.Split(*testBackends, ","))