Call disconnect callback on TLS error.

When using the library asynchronously, TLS errors caused e.g. because
of the date/time not set correctly, cause the connection to be silently
dropped without the disconnection callback being invoked, as described
in issue #1052.

This commit fixes the issue, returning the behavior to the one the
library had previous to version 1.5.4, if a TLS error occurs, the
disconnect callback will be invoked for the client to get notified of
the error.

Signed-off-by: doragasu <doragasu@protonmail.com>