Value initialized outside of Run gets reset

Please provide a succinct description of the issue.

#### Repro steps

Create an F# Timer function:

``` fsharp
open System

let epoch = DateTime(1970,1,1,0,0,0,DateTimeKind.Utc)

let Run(myTimer: TimerInfo, log: TraceWriter) =
log.Info(epoch.ToString())
```

#### Expected behavior

log should show the epoch as instantiated: `1/1/1970 12:00:00 AM`, in a fashion similar to what would be expected from a "regular" `.fsx` F# script.

#### Actual behavior

Function compiles and runs, but log show the epoch as `1/1/0001 12:00:00 AM`.

#### Known workarounds

- If I change the function to instantiate `epoch` inside the `Run` function, everything works as expected.
- If I modify the code to have epoch be the return value of another function like below, everything works fine:

``` fsharp
open System

let getEpoch () =
DateTime(1970,1,1,0,0,0,DateTimeKind.Utc)

let Run(myTimer: TimerInfo, log: TraceWriter) =
log.Info(getEpoch().ToString())
```

#### Related information

Provide any related information

* Programming language used : F#
* Links to source: source provided above.

Start by reproducing the supplied F# Timer function in the Azure Functions host and trace how the top-level epoch value is initialized before Run executes. No source file or test is named; done means the log preserves the initialized 1970 value without requiring initialization inside Run or through another function.

Written by the indexing model from the issue text.