tests: "grep -e" is not portable to all platforms

The "-e" option to grep is not needed unless specifying more than one
pattern, which we don't do.  Remove it to avoid restricting the tests on
platforms that do not have a grep that recognises "-e".

Signed-off-by: John Keeping <john@keeping.me.uk>
tests: make whitespace consistent

Signed-off-by: John Keeping <john@keeping.me.uk>
t0107-snapshot: add tests for ZIP archives

Signed-off-by: John Keeping <john@keeping.me.uk>