Fix: don't use newlines in logging message

Fix: don't use newlines in logging message

Using explicit newlines ('\n') in a logging messages breaks the
logging output and makes it unnecessarily harder to read and parse the
LTTng daemons' logs.

Moreover, it is unnecessary to escape multi-line string literals.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>