tests: Add github-#0103 test for next-attribute-not-working-...

Reported by: Kovács Bálint

Git bisect against this test says:

    $ git bisect bad
    302b2f8ff1497ec3d3c777d789ccdddff3de1b63 is the first bad commit
    commit 302b2f8ff1497ec3d3c777d789ccdddff3de1b63
    Author: Rob Day <rkd@rkd.me.uk>
    Date:   Fri Feb 15 00:43:41 2013 +0000

        Fixing errors when compiling with -Wall -Wextra

        git-svn-id: svn://svn.code.sf.net/p/sipp/code/sipp/trunk@629 \
          60913f6b-29f6-41b8-8391-1ad2d2d6c344
Reorder parentheses to fix issue with next attribute.

The gcc -Wall warning about missing parentheses was fixed by adding
them around the wrong operators.  After this changeset, the next
parameter works like it should again.

Reported by: Kovács Bálint (@kovacsbalu)
Closes: github-#0103.
Merge pull request #105 from SIPp/fix/next-attrib-fails-with-test-in-recv

Fix for github-#0103.