* Fix flag completion

The flag completion functions should not be stored in the root cmd.
There is no requirement that the root cmd should be the same when
`RegisterFlagCompletionFunc` was called. Storing the flags there does
not work when you add the the flags to your cmd struct before you add the
cmd to the parent/root cmd. The flags can no longer be found in the rigth
place when the completion command is called and thus the flag completion
does not work.

Also #1423 claims that this would be thread safe but we still have a map
which will fail when accessed concurrently. To truly fix this issue use a
RWMutex.

Fixes #1437
Fixes #1320

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

* Fix trailing whitespaces in fish comp scripts

Signed-off-by: Paul Holzinger <pholzing@redhat.com>