Re: [Libguestfs] [PATCH 2/2] actions: refactor available & feature_available

Refactor the internal_feature_available to return the result for just one group, so it is easier to know on the library side what was the actual error, and which group refers to; drop internal_available, as no more needed after this. On the library side, implement in available and feature_available the real logic to iterate through the requested group, and error out or return whether the groups are available. This also introduces caching for the features, so each needs to be queried just once in each appliance run. The result of this is that there should be much less communication with the daemon to know about available features; the downside is that queries for more than one group at once, not already cached, will be cause more queries to the daemon.