Show swift version and check if the same on hosts by using
`swift-recon --swift-version`.
Ex:
$ swift-recon --swift-versions
Versions matched (2.7.1.dev144), 0 error[s] while checking hosts.
or if differs
Versions not matched (2.7.1.dev144, 2.7.1.dev145),
0 error[s] while checking hosts.
Change-Id: I3c2e569f0c44168333251bb58bab4b5582e15a45