Change chained hooks nil check to correct function

[shivshav]

The nil check was incorrect, resulting in a panic if the following conditions hold true:

1. You have a PostRead hook func defined
2. You don't have a PostReadImmediate hook func defined
3. You use ChainLifecycleHooks to use multiple hooks

PostRead --> PostReadImmediate

Additionally, a few other hook functions had what I believe are incorrect nil checks.

• PreWrite: Was checking if PreProcessing was nil instead of PreWrite
• PostFanout: Was check if PostRead was nil instead of PostFanout

[stewartboyd119]

Looks good. Do you mind adding a unit test in lifecycle_test.go. It can be really light. Just basically invoking a lifecycle method for a lifecycle struct constructed with the ChainedLifecycle method. The invocation not panicking is good enough. The test's godoc can explain the test's purpose (Since people will likely be confused why there aren't any more meaningful assertions).

[stewartboyd119]

Actually. Nvm, I'll just merge and add the tests along with the changelog for version update

[stewartboyd119]

I'll go and add tests to protect against a ChainLifecycleHooks progression

[shivshav]

Apologies I didn't see this earlier @stewartboyd119 thanks for merging this in and adding tests!