Wrap bugzilla search with retry
Wrap bugzilla search with retry

Retry with backoff whenever `Bugzilla` `search` and `get_bugs` method
calls raise an error.

This is basically the same as
<https://github.com/openshift/li/pull/3173> except since it replaces an
existing retry construct that catches all exceptions, `retry_on_eof` is
now `retry_on_exception`, to preserve existing behavior.

dobbymoodge/sprint_tools,danmcp/sprint_tools,danmcp/sprint_tools,openshift/sprint_tools,openshift/sprint_tools,dobbymoodge/sprint_tools