Tests that cookies can be updated
Result of Network.setCookie: {
    id : <number>
    result : {
        success : true
    }
    sessionId : <string>
}
Cookies before update: Num of cookies 1
name: foo, value: bar1, domain: 127.0.0.1, path: /, session
Result of Network.setCookie to update existing one: {
    id : <number>
    result : {
        success : true
    }
    sessionId : <string>
}
Cookies after update: Num of cookies 1
name: foo, value: second bar2, domain: 127.0.0.1, path: /, session