This spins up a separate process to submit telemetry data rather than
blocking the execution the current mach command.
Although the initial Python process needs to wait for the second process
to complete prior to exiting, it releases control of the console once it
finishes executing Python code, so from the user's perspective, mahc command
completion is not blocked by submitting telemetry data.
MozReview-Commit-ID: FlKDYd6rNPc
