If an SDK is being updated, and another SDK version is attempted to be updated concurrently, the second operation is ignored, even if the first operation is sent to the background.
This is related to
TISTUD-149 - We may want to prevent multiple SDK simultaneous downloads.
Steps to Reproduce:
1. Install SDK from URL (Help > Install Specific Titanium SDK > Install from URL) from a branch such as 'master'.
2. While the first SDK is downloading, send that process to the background and repeat step 1 with another branch (such as '2.1.X').
The second SDK download is ignored and there is no user notification of failure.
Both SDKs should download simultaneously.