Tests: Blacklist tst_QHostInfo::abortHostLookupInDifferentThread

Remove the insignificant_test CONFIG option in favor of a BLACKLIST
file. This test has been found failing on OpenSuse in CI.

Change-Id: Ibc6af3c30277fec7e422e8bbeccd9437de2a61ce
Task-number: QTBUG-23837
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@theqtcompany.com>

tests/auto/network/kernel/qhostinfo/BLACKLIST

+# QTBUG-23837
+[abortHostLookupInDifferentThread]
+opensuse-13.1 64bit

tests/auto/network/kernel/qhostinfo/qhostinfo.pro

@@ -14,5 +14,3 @@ wince*: {
 
 # needed for getaddrinfo with official MinGW
 mingw:DEFINES += _WIN32_WINNT=0x0501
-
-linux-*:CONFIG+=insignificant_test    # QTBUG-23837 - test is unstable