fixing raid1-gpt to use variable rest of disk space

having issues with install, this is a new and unused gpt partitioning
file, changing the final /srv partitoin to the -1 variable commonly used
in raid1.cfg for this purpose.

Change-Id: I21f0318943c5fac892b8921d9cc4b576e21b45c2
RT: 7290
Merge "fixing raid1-gpt to use variable rest of disk space" into production