Fix fail_if_empty invocation with pipes
Fix fail_if_empty invocation with pipes

* Since $@ parameter may have pipe '|' it should be processed correctly.
  Currenly the part before pipe is assigned as $@ so bash runs pipe with
  commands after it after execution of function. However, we want to assign
  command with pipe to $@ thus "" around command with pipe are required.
* replace $() with eval as $() doesn't work correctly with pipe as it tries to
  escape pipe so output variable contains wrong data.
* This patch adds tonumber to first invocation

Change-Id: I958e14c0a4ea4b5782d2c74dc895471b0f70b875

dprince/tripleo-heat-templates,openstack/tripleo-heat-templates,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates