Add assertions and remove LOG_INFO from update_test

[apavlo]

There is a bunch of LOG_INFO debug statements in 'update_test.cpp'

https://github.com/cmu-db/peloton/blob/master/test/executor/update_test.cpp

We should replace them to LOG_DEBUG. This should be easy

[Traveler98]

I am new to this . I changed what you asked for here : master...Traveler98:patch-1
Hope I've done it right .
EDIT : I've made a pull request too .

[tli2]

Right now we are not actually testing anything in update_test due to the lack of assertions. We should change the printout messages to actually check results.

(Then replace LOG_DEBUG for whatever printout is left)