JCLOUDS-79: Fix cli start scripts for Windows

Works for me:
```
C:\...\bin>set OPTS=-Djclouds.provider=aws-s3 -Djclouds.identity=$IDENTITY -Djclouds.credential=$CREDENTIAL

C:\...\bin>jclouds.bat blobstore container-list
shell.bat: Ignoring predefined value for KARAF_HOME
log4j:WARN No appenders could be found for logger (org.jclouds.rest.internal.InvokeSyncToAsyncHttpMethod).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Authorization error: The AWS Access Key Id you provided does not exist in our records.
``