Fix KV del command validation error
Fix KV del command validation error

This has an explcit unit test already which somehow passes at least some of the time. I suspect it passes because under some conditions the actual KV delete fails and returns non-zero as well as printing the warning which is what is being checked for in the test.

For some reason despite working for quite some time like this, I now have a branch in which this test fails consistently. It may be a timing/env issue where another process running an agent causes the delete to be successful so the command returns a 0 by chance. Either way this is clearly wrong and fixing it stops the test being flaky in my branch.
scalp42/consul,hashicorp/consul,42wim/consul,42wim/consul,youhong316/consul,youhong316/consul,kingland/consul,vamage/consul,kingland/consul,youhong316/consul,scalp42/consul,kingland/consul,kingland/consul,calgaryscientific/consul,kingland/consul,calgaryscientific/consul,youhong316/consul,youhong316/consul,scalp42/consul,calgaryscientific/consul,scalp42/consul,vamage/consul,hashicorp/consul,hashicorp/consul,calgaryscientific/consul,42wim/consul,vamage/consul,scalp42/consul,calgaryscientific/consul,hashicorp/consul,vamage/consul,vamage/consul,42wim/consul,42wim/consul