(maint) allow a curl exit code of 28 (timeout) -- try at fixing a race in this one test
Merge pull request #1852 from kylog/maint/2.7.x/retry-curl-timeouts

(maint) allow a curl exit code of 28 (timeout) -- try at fixing a race i...
Bug #19414

This patch ensures that local groups can be modified regardless of
wheter or not the users are in LDAP.

This also adds the manages_members attribute to Linux systems
supporting gpasswd.