gvfs-test: Fix for Python 3.3
gvfs-test: Fix for Python 3.3

Use read() instead of readall() for reading from subprocess, as this is a
BufferedReader() now. This also works for older Python versions.

Also, add another missing Popen.stdin.flush(), like in the previous commit.

gicmo/gvfs,xkahn/gvfs-cmis,halfline/gvfs,halfline/gvfs,xkahn/gvfs-cmis,gicmo/gvfs,xkahn/gvfs-cmis,halfline/gvfs,gicmo/gvfs,xkahn/gvfs-cmis,gicmo/gvfs