Error counter should be reset is successful

[dthonon]

Currently, error counter is incremented at each error, even transient. It should be reset if a successful transmission occur, to avoid stopping after a few recovered transient errors.

[dthonon]

mentioned in commit 51acf4d

[dthonon]

Fixed in 51acf4d. Tested in case of error less transfer, but not in case of transient or permanent error on server side.