Dell EqualLogic MultiInstance Cinder

Bugzilla Link: https://bugzilla.redhat.com/show_bug.cgi?id=1105218
We had a discussion about this approach with @cwolferh, it seems that splitting the string by commas is currently the best possible solution.

However you might consider not filtering out the brackets? I guess you want to support syntax like `[a,b,c]`, but the syntax typed into Foreman for array parameters is `["a", "b", "c"]`, which will not be supported anyway by this, so maybe we could just split it by commas simply and support only `a,b,c` syntax for the parameters (e.g. if `[` appeared in san_password, it would be filtered out). I'll leave this up to your consideration.