Add SCR back to our host-configs

[kennyweiss]

A recent PR was added to revamp our SCR usage within SPIO (#251).

When reviewing it, we discovered that we are no longer testing SCR in any of our host-configs.

We should add SCR to our LLNL host-configs and to at least one docker-based host-config, if possible.

[kennyweiss]

Based on a comment from @nselliott, it looks like we need to add [email protected] or later.

[white238]

SCR was turned off in our builds again due to a series of problems in their Spack package. This should be handled separately.

Issue #661 PR disabled again #683

[nselliott]

SCR is now in several of the host-configs and is exercised in testing.