[Sanitizer] Always initialize a Symbolizer (even if 'symbolize' is false).

If 'symbolize' flag is not set, we still want to transform virtual address
to module+offset pair in the call to Symbolizer::SymbolizeCode().
See https://code.google.com/p/address-sanitizer/issues/detail?id=251 for
more details.

llvm-svn: 197491