Error out in cases when user attempts to create secret with incorrect json/yaml file format.

[Sangeetha Hariharan]

acorn version - v0.10.0-rc2-9-g43dbcbf4+43dbcbf4

Steps to reproduce the problem:

1. Create secret with incorrect json/yaml file format using --file option like

%cat test.yml
type: "opaque"
data:
-test1:         "value1"
-test2:         "value2"
%acorn secret create --file test.yml mytestsec
mytestsec
 % acorn secret reveal mytestsec                
NAME      TYPE      KEY       VALUE

2. Secrets get created with no data.

Expected Behavior:
Secret creation should error out stating that there was no data found to create secrets.