FIX: remove from _uncollected to top of _collect
FIX: remove from _uncollected to top of _collect

This correctly handles the edge case where there is an exception raised
while processing the describe or collect methods on a flyer.  Without
this (and the next commit) the failing flyer will be trapped in
`_uncollected` and be re-tried in the finally from call-to-call.

ericdill/bluesky,ericdill/bluesky