Revert "Drop 90 servers from rax-dfw"

This reverts commit 3faf809d61e7011daddd57508877c6037458441f.

The issues plaguing rax-dfw instance booting seem to have subsided
again, prior to the earlier change going into effect.

Change-Id: I3659f2f63586830b2d1a2afaba7e3f4a7e5911d7
Merge "Revert "Drop 90 servers from rax-dfw""