Service exits if exception during authentication.

[brett-smith]

We had a situation where a dbus client would lose connection to the EmbeddedDBusDaemon when coming out of hibernate. This happened on OS X, but presumably it's a possibility on other operating systems too.

For reference, here is the trace we got.

18 Jan 2022 07:01:48,123 [EmbeddedDBusDaemon-unix: {path=/tmp/dbus-DJVKKRECWC, guid=1a082ff10254aac4f742ad2bf2c68850, listen=true}] ERROR SASL  - Cannot create command.
java.io.IOException: Invalid Command BEGINl^A^A&^Dn^A^Ao^U/org/freedesktop/DBus^F^As^To
        at org.freedesktop.dbus.connections.SASL$Command.<init>(SASL.java:824)
        at org.freedesktop.dbus.connections.SASL.receive(SASL.java:243)
        at org.freedesktop.dbus.connections.SASL.auth(SASL.java:683)
        at org.freedesktop.dbus.connections.transports.AbstractTransport.authenticate(AbstractTransport.java:131)
        at org.freedesktop.dbus.connections.transports.AbstractTransport.connect(AbstractTransport.java:118)
        at org.freedesktop.dbus.bin.EmbeddedDBusDaemon.startListening(EmbeddedDBusDaemon.java:214)
        at org.freedesktop.dbus.bin.EmbeddedDBusDaemon.startInForeground(EmbeddedDBusDaemon.java:74)
        at java.base/java.lang.Thread.run(Thread.java:833)
18 Jan 2022 07:01:48,170 [DBusConnection] ERROR IncomingMessageThread  - FatalException in connection thread
org.freedesktop.dbus.exceptions.FatalDBusException: Underlying transport returned EOF (1)
        at org.freedesktop.dbus.connections.AbstractConnection.readIncoming(AbstractConnection.java:1154)
        at org.freedesktop.dbus.connections.IncomingMessageThread.run(IncomingMessageThread.java:40)
18 Jan 2022 07:01:48,171 [EmbeddedDBusDaemon-unix: {path=/tmp/dbus-DJVKKRECWC, guid=1a082ff10254aac4f742ad2bf2c68850, listen=true}] ERROR EmbeddedDBusDaemon  - Got uncaught exception
java.lang.NullPointerException: Cannot invoke "org.freedesktop.dbus.connections.SASL$SaslCommand.ordinal()" because the return value of "org.freedesktop.dbus.connections.SASL$Command.getCommand()" is null
        at org.freedesktop.dbus.connections.SASL.auth(SASL.java:684)
        at org.freedesktop.dbus.connections.transports.AbstractTransport.authenticate(AbstractTransport.java:131)
        at org.freedesktop.dbus.connections.transports.AbstractTransport.connect(AbstractTransport.java:118)
        at org.freedesktop.dbus.bin.EmbeddedDBusDaemon.startListening(EmbeddedDBusDaemon.java:214)
        at org.freedesktop.dbus.bin.EmbeddedDBusDaemon.startInForeground(EmbeddedDBusDaemon.java:74)
        at java.base/java.lang.Thread.run(Thread.java:833)
18 Jan 2022 07:01:48,172 [DBusConnection] INFO  Main  - Disconnected from Bus, retrying

The SASL chat was somehow getting corrupted, resulting in a failure in the accept loop on the server.

This PR now throws an exception if the SASL command is not valid. Also AuthenticationException is now caught higher up and the connection is also closed. This allows the loop to continue and accept more connections.