Correct invalid docstrings

Several warnings and errors are reported when the Keystone
documentation is built because the docstrings are not valid
reStructuredText. This makes it more difficult than necessary
for developers to validate that new changes are correct.

This change corrects the docstrings so that there are fewer
warnings and errors.

Change-Id: I2000a02d5d374749b2c611e63743d542b74e7fa0
Merge "Correct invalid docstrings"