Fix client default read timeout setting

[kobrineli]

Summary

In this PR I removed setting zero timeout in case of passed negative value.
The problem occurs when we call client.Dial:

1. Firstly here we call dial and sets default options, and when the ReadTimeout value is NoTimeout, we set it to zero.
2. Then, in client.Connect method, we call opt.setDefault as well here, but by this moment readTimeout had been already set to default value zero, and here it would be interpreted as time duration zero value and be set to DefaultReadTimeout.

To prevent this error it is sufficient just to remove setting ReadTimeout to zero and leave it with negative value, because here is the only place it is used and current check is enough.

[CLAassistant]

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