Add support for rdma cgroup

RDMA controller/cgroup support is added with Linux kernel 4.11.
It allows to limit RDMA/IB specific resources.
It is described at [1].

Add support to set rdma cgroup parameters and read statistics.

[1] https://www.kernel.org/doc/Documentation/cgroup-v1/rdma.txt

Signed-off-by: Parav Pandit <parav@mellanox.com>

.travis.yml

@@ -4,7 +4,7 @@ go:
 
 install:
     - mkdir -p $GOPATH/src/github.com/prometheus $GOPATH/src/github.com/opencontainers
-    - cd $GOPATH/src/github.com/opencontainers && git clone https://github.com/opencontainers/runtime-spec && cd runtime-spec && git checkout 96de01bbb42c7af89bff100e10a9f0fb62e75bfb
+    - cd $GOPATH/src/github.com/opencontainers && git clone https://github.com/opencontainers/runtime-spec && cd runtime-spec && git checkout fa4b36aa9c99e00c2ef7b5c0013c84100ede5f4e
     - cd $GOPATH/src/github.com/containerd/cgroups
     - go get -t ./...