* Remove gzip processing flow completely from rekor

Issue #208 reported different handling of gzipped content via fetch vs
direct upload to rekor server. The code should be consistent, regardless
of whether content was compressed or not - by always attempting to
verify the signature against the (unmodified) byte stream.

This patch removes the gzip decoding completely from rekor and verifies
the bytes supplied or referenced.

Also fixes issue in E2E tests where sending SIGKILL to watch process
caused message to be printed to stderr, which fails the test when
running on MacOS.

Fixes #208

Signed-off-by: Bob Callaway <bcallawa@redhat.com>

Signed-off-by: Bob Callaway <bcallawa@redhat.com>

Co-authored-by: Dan Lorenc <dlorenc@google.com>