cdms2 can only open cdscanned http files from the directory the file is at

```
cdscan -x test_dap.xml  http://opendap.nccs.nasa.gov:9090/dods/OSSE/G5NR/Ganymed/7km/0.0625_deg/inst/inst30mn_2d_aer1_Nx
```

start python

```
f=cdms2.open("./my.xml")
s=f["cosc"]
print s.shape
s2=s[0,0] #failed
```

```
f=cdms2.open("my.xml")
s=f["cosc"]
print s.shape
s2=s[0,0] #works
```
