tests: fix spurious failures with Solaris dmake

tests: fix spurious failures with Solaris dmake

Solaris Distributed Make, when run in parallel mode, can sprinkle
its standard output with lines like:

  hostname --> 2 jobs
  ...
  hostname --> Job output
  ...

This behaviour was causing spurious errors in some tests where we
compare the output of make with a known, expected value.  Fix that.

* tests/tap-doc.test: Before comparing the output from make with its
expected value, remove extra lines that could have been printed by
Solaris dmake.
* tests/tap-doc2.test: Likewise.