`make test` doesn’t fail if tests do

[Felipe Gasper]

1. Corrupt test/27-tab-between-cstrings.tpkg/27-tab-between-cstrings.db.
2. make test

OBSERVE:

** PASSED ** : 00 s : 26-loc-centimetre : Verify parsing of centimetres in LOC records.
!! FAILED !! : 00 s : 27-tab-between-cstrings : Check for GH 147 regression
** PASSED ** : 00 s : 60-compile-builddir : compile ldns in a separate build directory
** PASSED ** : 00 s : codingstyle : Check LDNS CodingStyle

PASSED: 18 (95 %)	FAILED: 1 (5 %)	unknown: 0 (0 %)

--------------- Start Output: 27-tab-between-cstrings ------------------
!! FAILED !!     !! FAILED !!
DateRunEnd: 0
BaseName: 27-tab-between-cstrings
Description: Check for GH 147 regression
DateRunStart: 0
--------------- Test Output ------------------
exit code: 1
--------------- End Output: 27-tab-between-cstrings ------------------

… but the make process ends with status 0.