fix: disconnect called before connection has completed #107

[Julusian]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

bug fix

• What is the current behavior? (You can also link to an open issue here)

fixes #107

The cause was the assignment of _socketProcess happening async, meaning that if disconnect or destroy was called before that promise had resolved, then it would look like connect had never been called, and the cleanup would be skipped

• What is the new behavior (if this is a feature change)?

There are two parts here.

1. _isDisconnecting is used by disconnect to skip the call to the threads connect method if disconnect is called while the thread is being created. Once the thread is created, disconnect previously operated as expected
2. _creatingSocket is used by destroy, so that it can wait for the thread creation to complete before attempting to destroy the thread. in the future, maybe this creation can be abortable, but that will require changes in threadedclass

• Other information:

Only given a very light synthetic test so far.