Allow custom values for different test types, i.e. ULT, AUB, etc. can
have custom timeout by using e.g.: NEO_{ULT,AUB,...}_ITERATION_MAX_TIME.
Old behavior with reading NEO_ULT_ITERATION_MAX_TIME for each test type
is preserved but new envirnoment variable has precedence.
Signed-off-by: Artur Harasimiuk <artur.harasimiuk@intel.com>