test: opt erasure-coding loopback clusters out of the remote endpoint guard

The erasure-coding suites drive VolumeEcShardsCopy / VolumeCopy between
volume servers bound to 127.0.0.1, which the copy/tail source guard now
rejects by default. Pass -volume.allowUntrustedRemoteEndpoints to the
test volume launches, matching what the volume_server framework
harnesses already do.

test/erasure_coding/multidisk_shell_lifecycle_test.go

@@ -233,6 +233,7 @@ func (c *MultiDiskCluster) startVolumeServers(ctx context.Context) error {
 			"-dir", strings.Join(diskDirs, ","),
 			"-max", strings.Join(maxVolumes, ","),
 			"-master", "127.0.0.1:9334",
+			"-volume.allowUntrustedRemoteEndpoints",
 			"-ip", "127.0.0.1",
 			"-dataCenter", "dc1",
 			"-rack", fmt.Sprintf("rack%d", i),