fix(H-Keyring): if getCache returns Error not EntryDoesNotExist, error

[texastony]

Issue #, if available:

Description of changes:
The Cache querying logic in the H-Keyring confuses a cache miss
with an opaque error.

i.e: getCachOutput.Failure? is not always EntryDoesNotExist but could be something like Opaque(obj? := java.nio.BufferUnderflowException).

Thus, I suggest we refactor the methods that call the cache to differentiate b/w Opaque and EntryDoesNotExist.

For an explanation on why we should never catch and swallow all exceptions/errors,
see: https://stackoverflow.com/questions/2416316/why-is-the-catchexception-almost-always-a-bad-idea

Finally, the behavior of the H-Keyring is possibly better respected by such a change.
The H-Kerying's specification reads:

If a cache entry is not found or the cache entry is expired, the hierarchical keyring MUST attempt to obtain the branch key materials by querying the backing branch keystore specified in the retrieve OnEncrypt branch key materials section.

The specification does not say it MUST swallow all exceptions.

Squash/merge commit message, if applicable:
fix(H-Keyring): if getCache returns Opaque Error, return Opaque

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[seebees]

This is a bending change that we can not make to our customers.

[seebees]

Given the number of people with custom caches that exist I'm ok.

However, we need to update put, and work out updating the DB-ESDK as well