tc: Optimize gact action lookup

tc: Optimize gact action lookup

When adding a filter with a gact action such as 'drop', tc first tries
to open a shared object with equivalent name (m_drop.so in this case)
before trying gact. Avoid this by matching the action name against those
handled by gact prior to calling get_action_kind().

Cc: Jiri Pirko <jiri@mellanox.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: David Ahern <dsahern@gmail.com>
Signed-off-by: Phil Sutter <phil@nwl.cc>