logging: move string to the beginning of msg

this allow (to some extents) to print log messages directly to
stdout and/or stderr without extra parsing.

NOTE:
- messages are sent from differnet threads and there for they are less readable
  when they arrive all together
- there is no printing of message level and subsystem

for simple coding/debugging purposes this is useful, but otherwise
look at how ping_test.c or kronosnetd create a logpipe and read
sequencial messages from there.

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>