chendo/tls: handshake_client.go; 38 LoC

Found a possible issue in [chendo/tls](https://www.github.com/chendo/tls) at [handshake_client.go](https://github.com/chendo/tls/blob/8f00496f7ae194842efc351085889cb2a771d4da/handshake_client.go#L351-L388)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first
issue it finds, so please do not limit your consideration to the contents of the below message.

> reference to chain is reassigned at line 377

[Click here to see the code in its original context.](https://github.com/chendo/tls/blob/8f00496f7ae194842efc351085889cb2a771d4da/handshake_client.go#L351-L388)

Click here to show the 38 line(s) of Go which triggered the analyzer.

```go
for i, chain := range c.config.Certificates {
if !rsaAvail && !ecdsaAvail {
continue
}

for j, cert := range chain.Certificate {
x509Cert := chain.Leaf
// parse the certificate if this isn't the leaf
// node, or if chain.Leaf was nil
if j != 0 || x509Cert == nil {
if x509Cert, err = x509.ParseCertificate(cert); err != nil {
c.sendAlert(alertInternalError)
return errors.New("tls: failed to parse client certificate #" + strconv.Itoa(i) + ": " + err.Error())
}
}

switch {
case rsaAvail && x509Cert.PublicKeyAlgorithm == x509.RSA:
case ecdsaAvail && x509Cert.PublicKeyAlgorithm == x509.ECDSA:
default:
continue findCert
}

if len(certReq.certificateAuthorities) == 0 {
// they gave us an empty list, so just take the
// first RSA cert from c.config.Certificates
chainToSend = &chain
break findCert
}

for _, ca := range certReq.certificateAuthorities {
if bytes.Equal(x509Cert.RawIssuer, ca) {
chainToSend = &chain
break findCert
}
}
}
}

```

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See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: 8f00496f7ae194842efc351085889cb2a771d4da