LogAudit.cpp: replace newlines with spaces in audit messages

Some kernels have a bug which causes a newline to show up in audit
messages. The embedded newlines cause one message to look like two due
to prefix controls.

Replace any newlines with spaces. Duplicate spaces are further
consolidated in code immediately after this newly added code.

Test: create an audit message with a newline, and watch it be cleaned up.
Bug: 27878170
Change-Id: Id90c29ab9e10d3be96f51403b0293622d782422a