When searching a list of directories, the files which match
the pattern are accumulated in a slice.  If the glob has a
wildcard for the directory, and the wildcard matches a file
rather than a directory, then the files found so far are
discarded.  E.g., path.Glob("*/x") in a directory which
contains both files and subdirectories.  This patch avoids
discarding matches found so far when a file is found.

R=r
CC=bsiegert, golang-dev
https://golang.org/cl/3015042