run_scripting cmd can't mute the pinger effectively

[wcpettus]

When we run the routine script, we should generically mute the pinger on the esr for the next one hour via something like:

- action: cmd
  cmds:
    - endpoint: pinger
      method_name: silence_ping
      value: [datetime.datetime.utcnow()+datetime.timedelta(0,3600)).strftime(constants.TIME_FORMAT)]
      timeout: 100

Fixing this is a two part-issue:

• run_scripting's action_cmd doesn't try asteval logic, so this would fail.
  • asteval string processing should probably be generically implemented as a separate method, rather than specifically implemented separately in action_set, etc.
• asteval explicitly blocks import and doesn't import datetime, so the generic asteval can't accomplish this anyway
  • we could fork our own version of asteval to add the datetime functions

[laroque]

The second point is solved by adding datetime to the asteval Interpretor's symtable

[laroque]

For point 1, it should probably be a different function, not just a method. The calibration decorator should also use it.

[wcpettus]

and for point 2, the solution Ben demonstrated interactively is:

In [1]: import asteval

In [2]: i = asteval.Interpreter()

In [3]: import datetime

In [4]: i.symtable['datetime'] = datetime

In [5]: i("datetime.datetime.now()")
Out[5]: datetime.datetime(2017, 12, 7, 18, 26, 47, 440703)

In [6]: i("(datetime.datetime.utcnow()+datetime.timedelta(1)).strftime('%Y-%m-%dT%H:%M:%SZ')")
Out[6]: '2017-12-08T18:27:40Z'

[wcpettus]

Specific problem fixed in v1.9.4, a generic implementation of astral should be discussed in a separate issue.