Node installer can't see Walrus in multi-network install

[Thierry Carrez]

On a classic multi-network topology:
CLC+Walrus <--- network1 ---> CC+SC <--- network2 ---> NC

Given how publication works (and by design), when you install the NC, the UEC installer can't see the CLC/Walrus.
The UEC installer will prompt the user for a distant CLC IP (which should be provided to it), then it knows about the CLC, the CC and the SC.
It presents the following message (from debian/eucalyptus-udeb.templates):

A Eucalyptus cloud controller was found, but no Walrus storage service.
 This installation will default to installing Walrus.
 If you wish, you may also install other Eucalyptus components on this
 machine.

That can be confusing, since Walrus may very well be already installed but just not detectable.
I propose we change the message to something that covers both cases, like:

A Eucalyptus cloud controller was detected, but no Walrus storage service.
 This might be because no Walrus is installed yet, or because the Walrus is already installed on a separate network.
 This installation will default to installing Walrus.
 If you wish, you may also install other Eucalyptus components on this
 machine.

[Thierry Carrez (ttx)]

In fact the current message is just:

A Eucalyptus cloud controller was found, but no Walrus storage service.
Cloud installation mode:
...

Given how eucalyptus-udeb.postinst works, it only imports the short description (first line) so there is no room for a longer explanation. Changing this now would break UIFreeze for all install screens of UEC, which does not seem warranted for such a wishlist fix.