package/libgcrypt: disable tests

Add a patch to disable tests as t-lock needs threads

Fixes:
 - http://autobuild.buildroot.org/results/50a8ba572e3fafd3c6a39bd54bcfcaf78b5ad325



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>