Set non-interactive default for set_security

Prior to this commit, fabric:set_security would default to interactive
IO priority. This would cause all nodes to set the security header
except shards on any nodes which were in MM. Subsequent calls to
fabric:get_security would cause inconsistent security properties to be
applied to the request. This patch sets a non-interactive default for
fabric:set_security, which will cause security updates to be applied to
all nodes regardless of MM by default.

BugzID: 28847
Merge pull request #150 from cloudant/28847-set_security-ignore-mm

Set non-interactive default for set_security