Update sanitizer_allocator to use new API.

Summary:
Update sanitizer_allocator to use new API.
    
Second patch in a series.  First patch https://reviews.llvm.org/D39072
    
Updates MmapNoAccess / MmapFixed call sites in the saniziter_allocator
to use the new Init/Map APIs instead.


Reviewers: alekseyshl, cryptoad, phosek, mcgrathr, dvyukov

Reviewed By: alekseyshl, cryptoad

Subscribers: dvyukov, mcgrathr, kubamracek

Differential Revision: https://reviews.llvm.org/D38592

llvm-svn: 317586