logger: return errno instead of bool
logger: return errno instead of bool

Return a errno instead of a bool so the upper layers have more
info and coding style is similar.

Signed-off-by: Mike Christie <39daeb1549a929782e38aa87c4e3da7f3844b09a@redhat.com>

open-iscsi/tcmu-runner,open-iscsi/tcmu-runner,agrover/tcmu-runner