Raise rather than generating millions of IPs.

Fixes bug #1163394

Formerly if we tried to create many millions of floating IPs with a
range like "192.168.2.224/2", address_to_hosts would happily iterate
over all of them (which would take a long time) and then nova-manage
would eventually crash with an OutOfMemoryError when we tried putting
all of them in a list.  Or, if the initial list wasn't quite big
enough to use all memory, it would blow up later (even more slowly)
when we tried to put them in the database via SQLAlchemy.

Now, raise exception.InvalidInput if the number of IPs is a million
or more.  (A million is erring on the side of caution.)

Change-Id: Ifc6b6a8faadc2e97e09f9f6c975e52229f705789
(cherry picked from commit 34de8d1529fb9a2e7fad096a6967b9a483ab0cb0)
import and install gettext in vm_vdi_cleaner.py

importing some nova modules expects _() to be defined, so lets define it
before we start importing them.

Change-Id: I7f951a24c19a53434c090cd2c01eded77c703943
(cherry picked from commit 205bda2cb52cb1c84e3f8b695a3df4d56b181143)
Merge "import and install gettext in vm_vdi_cleaner.py" into stable/grizzly
Merge "Raise rather than generating millions of IPs." into stable/grizzly