eldbus: Fix _eldbus_connection_send_and_block()

eldbus: Fix _eldbus_connection_send_and_block()

Some problems with the actual implementation:
- the reply should not be writable, as it can only be read.
- if an error happen dbus_connection_send_with_reply_and_block()
will return NULL so we need check before use it
- all other send calls remove one reference of the message

Now also it is creating a error message, so the caller can know why it fail.

@fix

Signed-off-by: Chris Michael <cp.michael@samsung.com>