vhost_user_block, virtio-devices, block_util: Extract common block code

Extract the code that is used by vhost_user_block from the
virtio-devices crate to remove the dependencies on unrequired
functionality such as the virtio transports.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

Cargo.lock

@@ -145,6 +145,19 @@ dependencies = [
  "constant_time_eq",
 ]
 
+[[package]]
+name = "block_util"
+version = "0.1.0"
+dependencies = [
+ "log 0.4.8",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "virtio-bindings",
+ "vm-memory",
+ "vm-virtio",
+]
+
 [[package]]
 name = "byteorder"
 version = "1.3.4"
@@ -1437,6 +1450,7 @@ dependencies = [
 name = "vhost_user_block"
 version = "0.1.0"
 dependencies = [
+ "block_util",
  "clap",
  "epoll",
  "libc",
@@ -1446,7 +1460,6 @@ dependencies = [
  "vhost",
  "vhost_user_backend",
  "virtio-bindings",
- "virtio-devices",
  "vm-memory",
  "vmm-sys-util",
 ]
@@ -1501,6 +1514,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "arc-swap",
+ "block_util",
  "byteorder",
  "devices",
  "epoll",