The `myArchive` static member of GerritLauncher is lazy initialized in
the `getDistributionArchive` method.
According to FindBugs:
Because the compiler or processor may reorder instructions, threads
are not guaranteed to see a completely initialized object, if the
method can be called by multiple threads.
Fix this by declaring the member as 'volatile'.
Change-Id: I2774cc12c2ee749331f72ff83c3d317b073787f3
c32be67180