Multiple completions do not work with 'allexport'

[nikitadanilov]

Describe the bug

If an interactive shell has set -a, completion functions are exported and inherited by spawned non-interactive shells, which typically do not have extglob. This results in spurious errors like

/bin/bash: _patch: line 3: syntax error near unexpected token `('
/bin/bash: _patch: line 3: ` --strip | --ifdef | --prefix | --basename-prefix | --suffix | --get | -!(-*)[pDBYzg])'
/bin/bash: error importing function definition for `_patch'

(Similarly for _sudo, _tar, etc.)

To reproduce

Add set -a to you .bashrc.