[global] make all utf-8 handling use errors='ignore'

Stop playing whack-a-mole with unicode handling and ignore all
invalid characters. It's not really possible to ensure that we
always get strict utf-8 data from the system - e.g. dmesg on
systems with broken BIOS strings will often spit undecodable
byte sequences.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>