[#1309] test: Clean up config after tests

Signed-off-by: Aleksey Savchuk <a.savchuk@yadro.com>

cmd/frostfs-cli/internal/key/key_test.go

@@ -24,6 +24,8 @@ var testCmd = &cobra.Command{
 }
 
 func Test_getOrGenerate(t *testing.T) {
+	t.Cleanup(viper.Reset)
+
 	dir := t.TempDir()
 
 	wallPath := filepath.Join(dir, "wallet.json")

cmd/frostfs-node/config/test/config.go

@@ -40,6 +40,15 @@ func ForEachFileType(pref string, f func(*config.Config)) {
 
 // ForEnvFileType creates config from `<pref>.env` file.
 func ForEnvFileType(t testing.TB, pref string, f func(*config.Config)) {
+	envs := os.Environ()
+	t.Cleanup(func() {
+		os.Clearenv()
+		for _, env := range envs {
+			keyValue := strings.Split(env, "=")
+			os.Setenv(keyValue[0], keyValue[1])
+		}
+	})
+
 	f(fromEnvFile(t, pref+".env"))
 }