When testing a connection the previous error message should be cleared

[hm]

When you test a connection and it fails an error message is displayed in the text box next to the test button. When changing settings and pressing test again, the same error message keeps displaying until the new test returns either true or an error message. If the same error message is displayed again then you are unsure if the test has run at all. When pressing the test connection button the text box should be cleared as the first thing, before running the actual test.

[jng]

Fixed r6490

[hm]

Please backport this to 4.0 branch

[jng]

Backported r6496