Fix misc OOM bugs

Fix misc OOM bugs

* tests/testutils.c: Run test function twice, once to prime it for
  static allocations, once to count the non-static allocations.
* tests/testutilsqemu.c: Initialize variable correctl
* src/capabilities.c: Don't free machines variable upon failure
  since caller must do that
* src/xm_internal.c: Add missing check for OOM in building VIF
  config param