[NativeProcessLinux] Remove logging and error callbacks

Summary:
These are remnants of the thread state coordinator, which are now unnecessary. I have basically
inlined the callbacks. No functional change.

Test Plan: Tests continue to pass.

Reviewers: chaoren, vharron

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D9343

llvm-svn: 236707