Don't drain Vecs
Don't drain Vecs

Drain is useful when removing a partial range from a collection, or to
keep the collection's memory allocation afterwards. This isn't the case
for these two spots, so we can just turn them into iterators more directly.

Signed-off-by: Andy Grover <b7d524d2f5cc5aebadb6b92b08d3ab26911cde33@redhat.com>

mulkieran/stratisd,stratis-storage/stratisd,stratis-storage/stratisd,stratis-storage/stratisd,mulkieran/stratisd,trgill/stratisd,trgill/stratisd