provider: IllegalStateException in getCowVirtualSize

Since JBoss 7.3 (httpclient 4.2) closing an InputStream might also
trigger IllegalStateException. As we were already catching IOException
we should now catch IllegalStateException too.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1022569
Change-Id: I20b816c49e60763f4f5b930f309365c0c770e1cd
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>