go client is not fooled by faketime

[jku]

There are a few tests that require faketime in the suite.

• test suite uses faketime to run clients-under-test at different times. faketime uses LD_PRELOAD tricks to intercept some system calls
• golang does not use those system calls

So the results from faketime tests are incorrect for go

TODO:

• fix the golang test client: maybe the test client could read the (faked) system time with by shelling out a "date +%s" and the library could offer some mechanism to set current date for test purposes?
• maybe add a test to make sure our time faking works: currently go client looks like it works but we don't actually know

[jku]

maybe add a test to make sure our time faking works: currently go client looks like it works but we don't actually know

I will do this bit

[jku]

Acoording to go-tuf docs Updater.UnsafeSetRefTime() exists. Possibly we only need to

• read the reference time using system call to date +%s in clients/go-tuf
• Use Updater.UnsafeSetRefTime() with that reference time
  `

[jku]

Yes, this can be worked arount in the test client: I will fix in #265