storage: get rid of 'servicevms' subdir

Keep all the non-template VMs in 'appvms'. Having it split makes no
sense since any VM can be "converted" to NetVM by simply changing its
provides_network attribute and probably assigning some PCI device.

On the other hand, it may be useful to set this manually, for example by
management stack - based on VM function, not type. But don't care about
it for now.

qubes/storage/__init__.py

@@ -507,7 +507,6 @@ class Pool(object):
 
             * ``appvms`` for ``QubesAppVm`` or ``QubesHvm``
             * ``vm-templates`` for ``QubesTemplateVm`` or ``QubesTemplateHvm``
-            * ``servicevms`` for any subclass of  ``QubesNetVm``
 
             Args:
                 vm: a QubesVM
@@ -517,20 +516,13 @@ class Pool(object):
                 string (str) absolute path to the directory where the vm files
                              are stored
         """
-        if vm.is_appvm():
-            subdir = 'appvms'
-        elif vm.is_template():
+        if vm.is_template():
             subdir = 'vm-templates'
-        elif vm.is_netvm():
-            subdir = 'servicevms'
         elif vm.is_disposablevm():
             subdir = 'appvms'
             return os.path.join(pool_dir, subdir, vm.template.name + '-dvm')
-        elif isinstance(vm, qubes.vm.adminvm.AdminVM):
-            subdir = 'servicevms'
         else:
-            raise qubes.exc.QubesException(
-                'unknown vm type: {!r}'.format(str(vm.__class__)))
+            subdir = 'appvms'
 
         return os.path.join(pool_dir, subdir, vm.name)