Refactor Load, Unload, and Swap Plugins tests in control_test.go. Added a function for retrying loading of a plugin to resolve timeout failures in travis.
Refactor Load, Unload, and Swap Plugins tests in control_test.go. Added
a function for retrying loading of a plugin to resolve timeout failures
in travis.

mjbrender/snap,mjbrender/snap,lynxbat/foo,sandlbn/snap,mkleina/snap,sandlbn/snap,intelsdi-x/snap,intelsdi-x/snap,lynxbat/foo,mkleina/snap