fix compile error when compiling column_predicate-test.cc
fix compile error when compiling column_predicate-test.cc

The test does not compile against boost 1.56. The error message is:

  gtest-printers.h:245: undefined reference to `std::basic_ostream<char,
  std::char_traits<char>>& boost::operator<< <char,std::char_traits<char>
  ,kudu::ColumnPredicate>>(std::basic_ostream<char,
  std::char_traits<char>>&, boost::optional<kudu::ColumnPredicate> const&)`

It appears to be https://svn.boost.org/trac/boost/ticket/10825, but
including optional_io.hpp in column_predicate.h (the purported workaround)
yields a different compile error:

  operator<<: cannot bind lvalue to 'std::basic_ostream<char>&&'

Rather than defining operator<< in ColumnPredicate, let's just modify the
ASSERTs in the test. I don't understand gtest macros well enough to know why
this helps, but I've verified that the modified test compiles and passes
when built against boost 1.56 and 1.58.

Change-Id: I6f9a9634eeccd86616be80b004ecce596155bb57
Reviewed-on: http://gerrit.cloudera.org:8080/3233
Tested-by: Kudu Jenkins
Reviewed-by: song bruce zhang <117031f27ae81d87659770823f997b096312aee1@gmail.com>
Reviewed-by: Dan Burkert <2591e5f46f28d303f9dc027d475a5c60d8dea17a@cloudera.com>

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