[asan] Fix 2 problems in nohugepage_test.
[asan] Fix 2 problems in nohugepage_test.

1. /proc/self/smaps may be bigger than 1 << 14.  On my machine, it is
26KB.
2. The read system call may return a partially filled buffer.  We need
to check the return value from read.

Patch by H.J. Lu


git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@231502 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