[smack] [cm] Gives Legato apps append access to "_"
[smack] [cm] Gives Legato apps append access to "_"

Smack distinguishes write and append operations. The smack
rule between labels "app.<appName>" and "_" is now only
"rwx". This creates problem for apps that manipulate files
using append instead of write.

For example, the command "cm data connect" is denied from
appending to the file /etc/resolv.conf with DNS info
("app.tools" on "_"). As a result, dnsmasq is not able to
perform DNS forwarding.

Giving additional append permission should bring minimal
impact to the system since there is already a write
permission granted.

Resolves: LE-13961
Related: LE-13807
Change-Id: I16b3ff48bc51b92c9fcd87f7f8df534fb39240b8

legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af