[ASan] Clear allocation magic value before recycling the chunk. This led to spurious crashes in LSan when it walked through reused chunks. Don't know how to create not-brittle test case for this.
[ASan] Clear allocation magic value before recycling the chunk. This led to spurious crashes in LSan when it walked through reused chunks. Don't know how to create not-brittle test case for this.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@184404 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt