Unify whitespace around *_ALLOW_THREADS macros
Unify whitespace around *_ALLOW_THREADS macros

Most of the code treats libvirt API calls as separate block, keeping one
blank line before the LIBVIRT_BEGIN_ALLOW_THREAD, and one blank line
after LIBVIRT_END_ALLOW_THREADS. Unify the whitespace so all calls
wrapped with these macros are treated as a separate block.

libvirt/libvirt-python,libvirt/libvirt-python,libvirt/libvirt-python