Handle ECONNREFUSED exception in SolidFire driver.

The SolidFire driver wasn't handling connection exceptions
during init (capacity updates from scheduler).

This patch add a try/except wrap around the two places
that this is called and logs and error rather than crashing
cinder-volume service.

Fixes bug: 1195910

Change-Id: I30347cc0973bbf9dbc30ea02e204560095fc75b4
(cherry picked from commit d596bfe6562307343858f419062756640000b0c8)