bgpd: Fix group overrides for AF flags/filters

bgpd: Fix group overrides for AF flags/filters

The previous commit introduced very strict unit tests which check all
three involved components (config input, config output, internal data
structures) which revealed two more bugs in the peer-group override
implementation.

This commit fixes overrides for 'allowas-in <number>' and
'unsuppress-map', which both had a small mistake/typo causing those
issues.

Signed-off-by: Pascal Mathis <mail@pascalmathis.com>