get_param calls with multiple arguments need brackets around them

get_param calls with multiple arguments need brackets around them

This issue was spotted during major upgrade where we had calls like
this:

   servers: {get_param: servers, Controller}

These get_param calls are hanging indefinitely and make the whole
upgrade end in a timeout. We need to put brackets around the get_param
function when there are multiple arguments:
http://docs.openstack.org/developer/heat/template_guide/hot_spec.html#get-param

This is already done in most of the tree, and the few places where this
was not happening were parts not under CI. After this change the
following grep returns only one false positive:

   grep -ir get_param: |grep -v -- '\[' |grep ','

Change-Id: I65b23bb44f37b93e017dd15a5212939ffac76614
Closes-Bug: #1626628