tests: fix conflict from parallelism in state store variables test (#26426)

The state store test for Variables check-and-set behavior for deletes uses the
same state store for a set of parallel tests. But one of the tests overlaps
another by using the same path, and this can cause spurious test failures by
hitting the CAS conflict error. This overlap doesn't appear to be intentional,
so change the test to use a different path.

Also cleaned up some unused test helpers in the same file.

nomad/state/state_store_variables_test.go

@@ -4,7 +4,6 @@
 package state
 
 import (
-	"encoding/json"
 	"errors"
 	"sort"
 	"strings"
@@ -735,22 +734,6 @@ func TestStateStore_ListVariablesByKeyID(t *testing.T) {
 	must.Eq(t, 5, count)
 }
 
-func printVariable(tsv *structs.VariableEncrypted) string {
-	b, _ := json.Marshal(tsv)
-	return string(b)
-}
-
-func printVariables(tsvs []*structs.VariableEncrypted) string {
-	if len(tsvs) == 0 {
-		return ""
-	}
-	var out strings.Builder
-	for _, tsv := range tsvs {
-		out.WriteString(printVariable(tsv) + "\n")
-	}
-	return out.String()
-}
-
 // TestStateStore_Variables_DeleteCAS
 func TestStateStore_Variables_DeleteCAS(t *testing.T) {
 	ci.Parallel(t)
@@ -822,7 +805,7 @@ func TestStateStore_Variables_DeleteCAS(t *testing.T) {
 	t.Run("real_locked_var-cas_0", func(t *testing.T) {
 		ci.Parallel(t)
 		sv := mock.VariableEncrypted()
-		sv.Path = "real_var/cas_0"
+		sv.Path = "real_locked_var/cas_0"
 		resp := ts.VarSet(10, &structs.VarApplyStateRequest{
 			Op:  structs.VarOpSet,
 			Var: sv,