Fix bugs in simplified test dependencies

Fix bugs in simplified test dependencies

Problem reported by Glenn Morris in:
http://lists.gnu.org/archive/html/emacs-devel/2017-04/msg00017.html
* test/Makefile.in (LOGFILES, TESTS): Omit leading "./".
(TESTS): Omit unnecessary patsubst.
(test_template): Redo dependency heuristic, hopefully
correctly this time.  It's the .log file that depends,
not the phony test target.  Declare the phonies to be PHONY.
Resurrect the exception for the *-tests subdirectory.
Adjust to the fact that leading "./" is omitted now.