That's strange. OSGi should be activating the plugin with the later version number. I'm not sure why it's not, but I will ask around. Maybe someone else at IBM has an idea.
Meanwhile, you could work around the problem by temporarily removing the earlier plugin. Is com.ibm.domino.das_9.0.1.v00_00_20150108-0821.jar on the file system? If so, do the following:
1) tell http q
2) Move com.ibm.domino.das_9.0.1.v00_00_20150108-0821.jar to a backup folder
3) load http
4) tell http osgi ss com.ibm.domino.das
That last step is just to verify there is only one DAS plugin left.