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

[chaosphere2112]

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

Migrated from: CDAT/cdat#1368

[dnadeau4]

Fix:
c26036e