This reverts commit 624f522e71.
As of I06e8cff035ecfaa651e215d7b18de5abc3a273c3 "registry_host" is now
using the OSLO opt type of HostAddressOpt. This type does now allow
square brackets.
Change-Id: Iedb38f63c045b1ac1dfadd68db63c47b1a0536da
Closes-Bug: #1711404