Searching for blobs based on tags doesn't work when the tag name consist of multiple words

Searching for blobs based on tags doesn't work when the tag name consist of multiple words, like e.g. `Malware scanning scan result='Malware'`.

For instance using the below URL (which works with the real azure storage) I get `400 InvalidQueryParameterValue` ... Probably caused by incorrect parsing of the %20 sequences in the `where` query parameter.

http://localhost:10000/devstoreaccount1/attachments?restype=container&comp=blobs&where=%22Malware%20Scanning%20scan%20result%22%3D%27Malware%27&maxresults=100