VFS-776 Slightly change how communication promises are fulfilled.
VFS-776 Slightly change how communication promises are fulfilled.

Because of an elusive, apparent standard library bug setting a promise
somehow invalidated the iterator for erasure. This change reorders
the operations so that the promise is first extracted from a map and
then fulfilled.


Former-commit-id: e9c66f087ab30b082e98a4cede7798c00b44a77e
onedata/helpers,onedata/oneclient,onedata/helpers,onedata/oneclient,onedata/oneclient,onedata/oneclient