specs-go/config: Make KernelTCP and ClassID omitempty
specs-go/config: Make KernelTCP and ClassID omitempty

Found with:

  $ git grep ' \*' origin/master -- specs-go/*.go | grep -v omitempty
  origin/master:specs-go/config.go:       KernelTCP *uint64 `json:"kernelTCP"`
  origin/master:specs-go/config.go:       ClassID *uint32 `json:"classID"`

Both settings are optional:

  $ git grep '`kernelTCP`\|`classID`' origin/master
  origin/master:config-linux.md:* **`kernelTCP`** *(uint64, optional)* - ...
  origin/master:config-linux.md:* **`classID`** *(uint32, optional)* - ...

Signed-off-by: W. Trevor King <f75897670c17327c42ab201733fb8a81ff9f4c34@tremily.us>

cloudfoundry-incubator/specs,hqhq/specs,hqhq/runtime-spec,ujuc/specs,jonboulle/specs,wking/opencontainer-runtime-spec,opencontainers/specs,opencontainers/runtime-spec,laijs/specs,wking/opencontainer-specs,vbatts/specs