net-wireless/unifi: don't use tomcat-native anymore

net-wireless/unifi: don't use tomcat-native anymore

Using tomcat-native seems to cause SSL problems on most unifi versions.
Removing dep and also adjusting the service start commands to hide the
system copy of tomcat-native in case it's already installed for other
reasons.

Closes: https://bugs.gentoo.org/659302
Package-Manager: Portage-2.3.40, Repoman-2.3.9