Revert "Add "reboot_instance" EC2 API test"

This reverts commit 120739800aac59875f2eef003f51bd2da1c1a5a4.

This test never worked well it hit bug #1352341.

Change-Id: Ia254c47119f8936c9f5b3ab60a8a2d75c10e32f2
Related-Bug: #1352341
Merge "Revert "Add "reboot_instance" EC2 API test""