Add parsing to extra-specs key check

Add parsing to extra-specs key check

When using the filter scheduler which is now the default,
we can no longer pass in extra-specs like: {minIOPS:500, ....},
because the capabilities filter will reject this because there is
no host reporting minIOPS:500 capabilities.

We now need to scope the keys (ie qos:minIOPS:500....), but
that unfortunately requires a fix to the SolidFire driver.

This change add a check for the ':' in the key, and parses
on it if it's there.

Also fixes backend_name and uses VERSION var instead of
generating string in stats reporting.

Fixes bug: 1167141

Change-Id: Ie7fd7d231af78cb18a13f44a4379b44d3c3385df