[docker] add ca-certificates to DEPS (#572)
[docker] add ca-certificates to DEPS (#572)

This allows initializing the submodules inside docker.
jwhui/borderrouter,openthread/borderrouter,openthread/borderrouter,bukepo/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/ot-br-posix,openthread/borderrouter,jwhui/borderrouter,bukepo/borderrouter,bukepo/borderrouter,jwhui/borderrouter,jwhui/borderrouter,jwhui/borderrouter,openthread/ot-br-posix,bukepo/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/ot-br-posix,openthread/ot-br-posix,bukepo/borderrouter,openthread/borderrouter