Fix for #3734 by synchronously creating the directories and #3735 by removing leftover files
from failed installations.

(Also includes a harmless update to the latest version of graceful-fs which has an updated readme)
Only log the error if there's actually an error.
Wraps mkdirsSync in a try/catch in case that fails.

This also pulls the code to remove a failed installation out into a separate function
rather than adding a third instance of the same code.
Merge pull request #3835 from adobe/dangoor/extension-directories

Extension Installation fixes: synchronous directory creation and remove leftover files