MFC r275907:

MFC r275907:

r275907 (by ngie):

  Fix building/installing tests when TESTSBASE != /usr/tests

  The work in r258233 hardcoded the assumption that tests was the last component
  of the tests tree by pushing tests as an explicit prefix for the paths in
  BSD.tests.dist and /usr was the prefix for all tests, per BSD.usr.dist and all
  of the mtree calls used in Makefile.inc1. This assumption breaks if/when one
  provides a custom TESTSBASE "prefix", e.g. TESTSBASE=/mytests .

  One thing that r258233 did properly though was remove "/usr/tests" creation
  from BSD.usr.dist -- that should have not been there in the first place. That
  was an "oops" on my part for the work that was originally committed in r241823

  Phabric: D1301
  Reviewed by: imp
  Sponsored by: EMC / Isilon Storage Division