Boolean options (such as "--protected" for glance md-namespace-update)
should accept a limited amount of valid values, rather than assuming an
"invalid" value means "False".
The following values (no matter the case) will now be interpreted as
True: ‘t’,’true’, ‘on’, ‘y’, ‘yes’, or ‘1’.
The following values (no matter the case) will now be interpreted as
False: ‘f’, ‘false’, ‘off’, ‘n’, ‘no’, or ‘0’.
Change-Id: I0e7942045d883ac398bab4a7a85f2b4ac9b1ed8c
Closes-Bug: #1607317
88e3b0ad98