Docs: consistency between man / --help

New functionality in hack/man-page-checker: start cross-
referencing the man page 'Synopsis' line against the
output of 'podman foo --help'. This is part 1, flag/option
consistency. Part 2 (arg consistency) is too big and will
have to wait for later.

flag/option consistency means: if 'podman foo --help'
includes the string '[flags]' in the Usage message,
make sure the man page includes '[*options*]' in its
Synopsis line, and vice-versa. This found several
inconsistencies, which I've fixed.

While doing this I realized that Cobra automatically
includes a 'Flags:' subsection in its --help output
for all subcommands that have defined flags. This
is great - it lets us cross-check against the
usage synopsis, and make sure that '[flags]' is
present or absent as needed, without fear of
human screwups. If a flag-less subcommand ever
gets extended with flags, but the developer forgets
to add '[flags]' and remove DisableFlagsInUseLine,
we now have a test that will catch that. (This,
too, caught two instances which I fixed).

I don't actually know if the new man-page-checker
functionality will work in CI: I vaguely recall that
it might run before 'make podman' does; and also
vaguely recall that some steps were taken to remedy
that.

Signed-off-by: Ed Santiago <santiago@redhat.com>

docs/source/markdown/podman-container-exists.1.md

@@ -4,7 +4,7 @@
 podman-container-exists - Check if a container exists in local storage
 
 ## SYNOPSIS
-**podman container exists** [*options*] *container*
+**podman container exists** *container*
 
 ## DESCRIPTION
 **podman container exists** checks if a container exists in local storage. The **ID** or **Name**