roachprod: do not mutate EBSVolumes

Previously, `roachprod create` appended volumes to
`providerOpts.EBSVolumes`, assuming it's done once per run. In reality,
the code is run every time when we create an instance, which leads to data
races and accumulation of extra EBS volumes.

This patch creates a copy of `providerOpts.EBSVolumes` before making any
changes to it.

Release note: None

pkg/roachprod/vm/aws/aws.go

@@ -921,20 +921,21 @@ func (p *Provider) runInstance(
 	if p.IAMProfile != "" {
 		args = append(args, "--iam-instance-profile", "Name="+p.IAMProfile)
 	}
-
+	// Make a local copy of providerOpts.EBSVolumes to prevent data races
+	ebsVolumes := providerOpts.EBSVolumes
 	// The local NVMe devices are automatically mapped.  Otherwise, we need to map an EBS data volume.
 	if !opts.SSDOpts.UseLocalSSD {
-		if len(providerOpts.EBSVolumes) == 0 && providerOpts.DefaultEBSVolume.Disk.VolumeType == "" {
+		if len(ebsVolumes) == 0 && providerOpts.DefaultEBSVolume.Disk.VolumeType == "" {
 			providerOpts.DefaultEBSVolume.Disk.VolumeType = defaultEBSVolumeType
 			providerOpts.DefaultEBSVolume.Disk.DeleteOnTermination = true
 		}
 
 		if providerOpts.DefaultEBSVolume.Disk.VolumeType != "" {
 			// Add default volume to the list of volumes we'll setup.
-			v := providerOpts.EBSVolumes.newVolume()
+			v := ebsVolumes.newVolume()
 			v.Disk = providerOpts.DefaultEBSVolume.Disk
 			v.Disk.DeleteOnTermination = true
-			providerOpts.EBSVolumes = append(providerOpts.EBSVolumes, v)
+			ebsVolumes = append(ebsVolumes, v)
 		}
 	}
 
@@ -946,9 +947,9 @@ func (p *Provider) runInstance(
 			DeleteOnTermination: true,
 		},
 	}
-	providerOpts.EBSVolumes = append(providerOpts.EBSVolumes, osDiskVolume)
+	ebsVolumes = append(ebsVolumes, osDiskVolume)
 
-	mapping, err := json.Marshal(providerOpts.EBSVolumes)
+	mapping, err := json.Marshal(ebsVolumes)
 	if err != nil {
 		return err
 	}