Bugfix: Store Thycotic object in an instance scope variable, not global.

Storing the 'Thycotic' object in a GLOBAL scoped variable is dangerous
in threaded code. Storing it as an INSTANCE variable is safer, and
provides the same functionality of making sure we create a single
Thycotic object and use it for as long as possible before having to
create another one.

Change-Id: I04c39889ee3176f8c1734cc3277bae78b6026821
Merge "Bugfix: Store Thycotic object in an instance scope variable, not global."
Refactor the getSecret() method to use several private methods.

This change cleans up the getSecret() method and moves the begin/rescue
blocks into individual methods for each part of the process:
  - getting from the short term cache
  - getting from the API
  - getting from the long term cache

Change-Id: Icf928733771aeff8d5a8c955e73d3a224d7dfb95
Merge "Refactor the getSecret() method to use several private methods."