Because --readonly is default true, passing something like
--disallow-deletes=false would not actually update that
value because the readonly flag would override. this makes it
so that the --disallow-* flags override the --readonly and
--writeonly flags.
Also fixes some minor formatting issues with share like an
extra space after the "Public Access:" entry.
Simplifies the handling of the explicit "none" by making the
flags for the dates optional and using nil to signify that
the value was left unset.
Bump the go.mod to go1.18 to enable the use of generics and
add a small generic function. This can easily be backed out
if it causes problems.
Change-Id: I1c5f1321ad17b8ace778ce55561cbbfc24321a68
f2fdd6ca33