This patch cleans up pkg/util/mount/* and pkg/util/volume/* to always
use filepath.Join instead of path.Join. filepath.Join is preferred
because path.Join can have issues on Windows.
This change queries the StorageOS API to retrieve the volume
device dir when a volume is attached, rather than relying on
the default /var/lib/storageos/volumes directory. This allows
all or some nodes to have kubelet running in a container with
the StorageOS volume path mounted in, which is required for
Azure ACS support.
Volume mount options are also supported.
