testsuite fails on hppa

According to https://buildd.debian.org/status/package.php?p=tor&suite=sid, 0.2.8.6 failed to build on hppa:

rend_cache/store_v2_desc_as_client: 
  FAIL ../src/test/test_rendcache.c:201: assert(ret OP_EQ -1): 0 vs -1
  [store_v2_desc_as_client FAILED]