[Minor] A few typos in comments and log messages

Author: Andrew Or <andrewor14@gmail.com>
Author: Andrew Or <andrew@databricks.com>

Closes #3021 from andrewor14/typos and squashes the following commits:

daaf417 [Andrew Or] Merge branch 'master' of github.com:apache/spark into typos
4838ae4 [Andrew Or] Merge branch 'master' of github.com:apache/spark into typos
026d426 [Andrew Or] Merge branch 'master' of github.com:andrewor14/spark into typos
a81ae8f [Andrew Or] Some typos