Extension update on failure return based reporting

[larohra]

Description

Currently the update sequence of an extension consists of the following operations -
Disable (OV) -> Update (NV) -> Uninstall (OV) -> Install if updateMode == UpdateWithInstall (NV) -> Enable (NV).

This PR addresses the issue where Extension Updates are blocked if there's any failure in the old version of the Extension. We've introduced a new flag 'continueOnUpdateFailure' which can be set in the new HandlerManifer of the extension to unblock the extension update.

Issue #

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• New Unit tests were added for the changes made and Travis.CI is passing.

Quality of Code and Contribution Guidelines

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This change is 

[pgombar]

LGTM with one suggestion