ID 561752 - A publish for a sequence revision can be started multiple times

Problem summary
A publish for a sequence revision can be started multiple times
 
Customer reported version
flix_6.6.2
 
Customer reported platform
 
Steps to reproduce
 
1)Import a large number of panels 150+ (this is so the publish takes longer, it will likely fail with fewer panels too)

2)Save the sequence and publish it.

3)Do either:
a) Reload the sequence revision interface and click publish again.
b)Ask another Flix user to go to the same sequence revision and publish it.
 
Expected behaviour
Flix should report that the sequence revision is currently being published
 
Actual behaviour
A new publish for the same sequence revision is started
 
Workaround
Unknown.
 
Reproduced by support
6.6.2-1
7.0.0 Beta (build 582)