Fix error message in daemonise.py
Fix error message in daemonise.py

The logging.error function does not understand old Python 2.x string
formatting.  Use Python 2.7/3.x formatting instead so the string is
already formatted when passed to the logger.

Change-Id: I0e3470f29eba17e676f09d18095120b3d325d133
Signed-off-by: Guillaume Tucker <e7e20b7c30f19d4ca6b81319ef81bf200369d137@collabora.com>

Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server