ipfs diags sys memory info is unclear for swap and virt

#### Version information:
`
root@ipfs-standalone:~# ipfs version --all
go-ipfs version: 0.4.15-
Repo version: 6
System version: amd64/linux
Golang version: go1.10.2
root@ipfs-standalone:~#
`
#### Type:
Bug

#### Description:
**Problem Statement:**

When executing "ipfs diag sys" on a system with 1GB swap, the utility shows 0 swap.

**Details:**

1. No similar issue appears to exist at this time.
2. The following output was captured from the utility:

`root@ipfs-standalone:~# ipfs diag sys
{"diskinfo":{"free_space":8151420928,"fstype":"61267","total_space":8134643712},"environment":{"GOPATH":"","IPFS_PATH":""},"ipfs_commit":"","ipfs_version":"0.4.15","memory":{"swap":0,"virt":557232000},"net":{"interface_addresses":["/ip4/127.0.0.1","/ip4/10.0.2.15","/ip6/::1","/ip6/fe80::40:c1ff:fefa:9bf5"],"online":true},"runtime":{"arch":"amd64","compiler":"gc","gomaxprocs":2,"numcpu":2,"numgoroutines":3451,"os":"linux","version":"go1.10.2"}}
`
3. The following was captured from the machine:
`
root@ipfs-standalone:~# cat /proc/swaps
Filename Type Size Used Priority
/swap.img file 1048572 352 -1
root@ipfs-standalone:~#
`
**Note: I have forked the repo and intend to research further and will update this issue accordingly. To do anything less would just be complaining. ;-)**