As non-gzipped trace files cause import-trace to always import zero
events, the input file is now openend as in the dump-trace tool, where
opening non-gzipped files obviously works fine.
In the medium term we should find a centralized solution for this,
instead of re-implementing it all over the place.
Change-Id: I75845c03c0bbdc2b6b578b83d492b7dbbb40f051