rest_dbus: get_host_interface: Iterate through busnames
rest_dbus: get_host_interface: Iterate through busnames

The mapper may return multiple busnames, as it's the case for an
object that has associations. So if the path is not found on the
busname, continue to see if there are more busnames to try instead
of quitting on the first try.

Fixes: openbmc/openbmc#3460

Tested: Verified the software interfaces are working again, and
that a dummy busname still raises an exception for the case where
none of the busnames returned by the mapper hold the requested
path.

Change-Id: Iaf36dd94f728d147f20c23666e5c19062b33f97a
Signed-off-by: Adriana Kobylak <742cf4d8dead98b4cab50b088fd2a1406293c958@us.ibm.com>

openbmc/phosphor-rest-server,openbmc/phosphor-rest-server