IsObjectFound function should not bury unexpected errors

[jgwest]

What type of PR is this?
/kind bug

What does this PR do / why we need it:

Currently, the IsObjectFound utility function is used to check whether a particular object exists on the cluster. It is used across the codebase, and with many different types of objects.

Unfortunately, IsObjectFound is making an incorrect assumption: this function assumes that ANY error that occurs (besides is not found) should be treated the same as the object not existing.

For example:

Cause	Return value
A) No error on Get object call	IsObjectFound returns true
B) Not found error on Get object call	IsObjectFound returns false
C) Any other error occurs on Get object call (network error, permission error, TLS error, etc)	IsObjectFound returns false

Notice that B and C, despite very different causes, return the same false of false.

This PR updates the function signature of IsObjectFound to return (rather than burying) the error, and updates all locations in the code where it is called.