Reduce travis-ci log output

Travis-ci log output is huge and overflows internal travis-ci view,
which makes it hard to find errors.
Redirect some output to a file and dump it only if it fails.
Remove "v" option from tar that builds and extracts the srcdist.
While running the tests manually, some non-POSIX (bashisms) with ==
vs = came to light.

Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5555)