Add failed to open stream to ConnectException

[sm2017]

When connect_timeout is reached I see the following error but isConnectionError is false

Error creating resource: [message] fopen(url): failed to open stream: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

[kstich]

failed to open stream can happen for a multitude of reasons. It seems pretty explicitly safe to use connection attempt failed as the determining factor here.

[sagikazarmark]

@kstich sounds better

[sm2017]

@kstich thank you

[sm2017]

@guzzle Can you accept the PR?

[sagikazarmark]

Will be reviewed when someone gets there, but I wouldn't expect it to be released for another few weeks. There are some other changes in the pipe too.

[sagikazarmark]

Thanks