storage: Convert virStoragePoolObjList to use virObjectRWLockable

storage: Convert virStoragePoolObjList to use virObjectRWLockable

Now that we have a private storage pool list, we can take the next
step and convert to using objects. In this case, we're going to use
RWLockable objects (just like every other driver) with two hash
tables for lookup by UUID or Name.

Along the way the ForEach and Search API's will be adjusted to use
the related Hash API's and the various FindBy functions altered and
augmented to allow for HashLookup w/ and w/o the pool lock already
taken.

After virStoragePoolObjRemove we will need to virObjectUnref(obj)
after to indicate the caller is "done" with it's reference. The
Unlock occurs during the Remove.

The NumOf, GetNames, and Export functions all have their own callback
functions to return the required data and the FindDuplicate code
can use the HashSearch function callbacks.