[NFC][Sanitizer] Change "return type" of INTERCEPT_FUNCTION to void

This temporary change tells us about all the places where the return
value of the INTERCEPT_FUNCTION macro is actually used. In the next
patch I will cleanup the macro and remove GetRealFuncAddress.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D61145

llvm-svn: 359325