NOTE: backporting BUG#42150 into next-mr
      Includes latest Andrei's patch (see [2 Feb 18:40] Bugs System)
      and merge.test post-push fix (see [3 Feb 18:04] Bugs System)

The reason of the bug appeared to be overreacting on absense of a
binlog file although the file name had been presented in in the master
binlog index file.
By convention, there should have been only a warning printed and the rest of
`reset master' logics completed.  This did not happen on windows
due to incorrect value of my_errno returned from nt_share_delete().
      
Fixed with correcting my_errno assignment in nt_share_delete() to be ENOENT in 
he event of no binlog file. Some minor refactoring has been made.