optimize cloning during highstate() runs

[noelmcloughlin]

I am using salter.sh script on project opensds/opensds-installer/salt/.

The opensds-formula is cloned on every execution of highstate() function. See logs: https://github.com/opensds/opensds-installer/pull/256#issuecomment-518171062

This wastes resources and needs to be optimized.

+ '[' -f /srv/salt//community/opensds/opensds-installer/salt/file_roots/install/auth.sls ']'
+ cp /srv/salt//community/opensds/opensds-installer/salt/file_roots/install/auth.sls /srv/salt//top.sls
+ break
+ '[' -z '' ']'
+ set +xv
cloning opensds-formula from saltstack-formulas ...             <==== this is the problem!!

[noelmcloughlin]

if (cycle == 1) clone else skip