rest-api: key missing for per "rx" and "rwx"

commit 85a1cf31e6 and db266a3fb2 introduce new per "rx" and "rwx", but key missing for per "rx" and "rwx" in permmap

Signed-off-by: Ailing Zhang <ailzhang@cisco.com>
Merge pull request #1880 from ailzhang/patch-1

rest-api: key missing for per "rx" and "rwx"

Backport: firefly
Reviewed-by: Sage Weil <sage@inktank.com>