unset XDG_HOME_CONFIG as gitea manages configuration locations (#33067)

unset XDG_CONFIG_HOME early to enable gitea to manage git configuration.
simple error checking to satisfy the linting. Closes #33039

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

models/unittest/testdb.go

@@ -59,6 +59,7 @@ func InitSettings() {
 	_ = hash.Register("dummy", hash.NewDummyHasher)
 
 	setting.PasswordHashAlgo, _ = hash.SetDefaultPasswordHashAlgorithm("dummy")
+	setting.InitGiteaEnvVars()
 }
 
 // TestOptions represents test options