[Java] Upgrade to Mockito 2.7.20.
[Java] Upgrade to Mockito 2.7.20.

galderz/Aeron,mikeb01/Aeron,oleksiyp/Aeron,EvilMcJerkface/Aeron,real-logic/Aeron,galderz/Aeron,real-logic/Aeron,oleksiyp/Aeron,mikeb01/Aeron,EvilMcJerkface/Aeron,real-logic/Aeron,mikeb01/Aeron,galderz/Aeron,real-logic/Aeron,EvilMcJerkface/Aeron,galderz/Aeron,mikeb01/Aeron,EvilMcJerkface/Aeron,oleksiyp/Aeron