fix incorrect use of loop variable (#16872)

This fixes a couple of references to loop variables in parallel tests
and deferred functions. When running a parallel test (calling
`t.Parallel()`) combined with the table-driven pattern, it's necessary
to copy the test case loop variable, otherwise only the last test case
is exercised. This is documented in the `testing` package:

https://pkg.go.dev/testing#hdr-Subtests_and_Sub_benchmarks

`defer` statements that invoke a closure should also not reference a
loop variable directly as the referenced value will change in each
iteration of the loop.

Issues were automatically found with the `loopvarcapture` linter.

command/kv_test.go

@@ -716,6 +716,7 @@ func TestKVPatchCommand_ArgValidation(t *testing.T) {
 	}
 
 	for _, tc := range cases {
+		tc := tc // capture range variable
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()