Ceph Cluster Performance Input Plugin

The existing ceph input plugin only has access to the local admin daemon socket
on the local host, and as such has access to a limited subset of data.  This
extends the plugin to use CLI commands to get access to the full spread of Ceph
data.  This patch collects global OSD map and IO statistics, PG state and per pool
IO and utilization statistics.

closes #1513

plugins/inputs/ceph/ceph_test.go

@@ -65,12 +65,17 @@ func TestFindSockets(t *testing.T) {
 		assert.NoError(t, err)
 	}()
 	c := &Ceph{
-		CephBinary: "foo",
-		SocketDir:  tmpdir,
+		CephBinary:             "foo",
+		OsdPrefix:              "ceph-osd",
+		MonPrefix:              "ceph-mon",
+		SocketDir:              tmpdir,
+		SocketSuffix:           "asok",
+		CephUser:               "client.admin",
+		CephConfig:             "/etc/ceph/ceph.conf",
+		GatherAdminSocketStats: true,
+		GatherClusterStats:     false,
 	}
 
-	c.setDefaults()
-
 	for _, st := range sockTestParams {
 		createTestFiles(tmpdir, st)