OC-4235: 'delay-loading' changes to reduce load-time

Here are findings,

knife-core(no-plugins)

    real    0m0.744s
    user    0m0.688s
    sys     0m0.052s
knife(with knife-google, knife-hp, knife-ec2, knife-windows,knife-terremark)
# before changes, 
    real    0m2.421s
    user    0m2.272s
    sys     0m0.140s

# After changes, 
    real    0m1.403s
    user    0m1.312s
    sys     0m0.072s
Environment:
1. Chef Version: 10.14.2
2. Ruby Version: 1.9.3p194
3. Gem Version: 1.8.24