The `myHome` static member of GerritLauncher is lazy initialized in
the `getHomeDirectory` 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: If2fd90ce83d5b383539aac41dddcacaca1729300
54c874b7b0