add_all_tests: removed trailing list seperator
add_all_tests: removed trailing list seperator

fixes cmake-warning:
CMake Warning (dev) at .../cmake-3.2.2/share/cmake-3.2/Modules/CMakeParseArguments.cmake:125 (list):
  Policy CMP0007 is not set: list command no longer ignores empty elements.
  Run "cmake --help-policy CMP0007" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.  List has value =
  [ENVIRONMENT;ARGS;].
Call Stack (most recent call first):
  tests/CMakeLists.txt:11 (cmake_parse_arguments)
  tests/CMakeLists.txt:44 (add_all_tests)
  tests/CMakeLists.txt:229 (add_test_executable)
This warning is for project developers.  Use -Wno-dev to suppress it.

hoangmle/metaSMT,nbruns1/metaSMT,hoangmle/metaSMT,finnhaedicke/metaSMT,agra-uni-bremen/metaSMT,nbruns1/metaSMT,finnhaedicke/metaSMT,nbruns1/metaSMT,finnhaedicke/metaSMT,agra-uni-bremen/metaSMT,agra-uni-bremen/metaSMT,hoangmle/metaSMT