schema/defs-linux: Fix type for seccomp names
schema/defs-linux: Fix type for seccomp names

The:

  "type": [
    "string"
  ]

syntax added in 652323cd (improve seccomp format to be more
expressive, 2017-01-13, #657) is not valid:

  $ ./validate ./config-schema.json <../config.json
  The document is not valid. see errors :
  - linux.seccomp.syscalls.0.names: Invalid type. Expected: string, given: array

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

hqhq/runtime-spec,wking/opencontainer-runtime-spec,hqhq/specs,laijs/specs,opencontainers/runtime-spec,opencontainers/specs,wking/opencontainer-specs