Lsm snapshot update check only, review changes.

@agorrod, here are my suggestions for your consideration.

First, I would move the `WT_CBT_CONFLICT_CHECK` into the `WT_CURSOR` structure (with a minor name change so it's not too long).  It seems to me the `WT_CURSOR_BTREE` flags are more about things going on in the structure itself rather than the operation the cursor is performing, and it seems to me like we're creating a "conflict check" cursor operation here.  I realize that's a fine line to draw, and I don't mind at all if you and @michaelcahill decide I'm on the wrong side of that line.

Second, I think we have to check if `cbt->ins` is non-NULL before indirecting through it, if the row-search routine returns an exact match from somewhere other than an insert list, I would expect `cbt->ins` to be NULL.

Third, while looking at the lsm changes, I tossed in a couple of gratuitous white-space cleanups as a separate commit.