Staging: hv: util: kvp: Fix the reported OSVersion string

The current win7 host does not like it when we return the
complete kernel release information. Conform to what the host
expects.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>