Since the deallocator is passed into the constructor of
a hash table it is not desirable to pass it into each
function again. Remove it from all functions, but provide
a virHashSteal to allow a item to be removed from a hash
table without deleteing it.

* src/util/hash.c, src/util/hash.h: Remove deallocator
  param from all functions. Add virHashSteal
* src/libvirt_private.syms: Add virHashSteal
* src/conf/domain_conf.c, src/conf/nwfilter_params.c,
  src/nwfilter/nwfilter_learnipaddr.c,
  src/qemu/qemu_command.c, src/xen/xm_internal.c: Update
  for changed hash API