connectionmanager: remove connecton if TLS negotiation fails

If a TLS handshake was failing, the device information was not
correctly removed, causing a connection to be detected and further
communications to fail.
So, while monitoring, some connections were stuck in "Connecting TLS".

Moreover, remove waitForReady because it's unused

Change-Id: I8350d7f8731311ab46db78fb26328edc0dcb31dc