packagers: dnf: improve logging support
packagers: dnf: improve logging support

dnf sends exception information in logging.
dnf uses sub debug level for its own debugging.

Change-Id: I9c42985d903418a1d1baef4355c768a95a230fe8
Signed-off-by: Alon Bar-Lev <2e3ceb4d37adc6ae3ccc00d3646e0e0a036ace03@redhat.com>

alonbl/otopi,alonbl/otopi,alonbl/otopi