Fix ExponentialReconnectionPolicy not incrementing correctly

[bahadir]

ExponentialReconnectionPolicy doesn't honor the number of retries made, since it uses the wrong argument for the attempt count.

Test code:

package main

import (
	"fmt"
	"github.com/gocql/gocql"
)

func main() {
	policy := gocql.ExponentialReconnectionPolicy{
		MaxRetries: 10,
	}

	for index := 0; index < 10; index++ {
		fmt.Println(policy.GetInterval(index))
	}
}

Before changes:

51.210466028s
51.244050908s
51.216456005s
51.193771418s
51.192463749s
51.218682307s
51.156563701s
51.165651925s
51.159696951s
51.180091186s

After changes:

60.466028ms
144.050908ms
216.456005ms
393.771418ms
792.463749ms
1.618682307s
3.156563701s
6.365651925s
12.759696951s
25.580091186s

[martin-sucha]

Thanks! Looks good to me. I don't have write access to this repo, so we need to wait for one of the maintainers to merge it though.

[alourie]

Great catch! Thanks!