net/sched: act_ipt: fix refcount leak when replace fails

After commit 4e8ddd7f ("net: sched: don't release reference on action
overwrite"), the error path of all actions was converted to drop refcount
also when the action was being overwritten. But we forgot act_ipt_init(),
in case allocation of 'tname' was not successful:

 # tc action add action xt -j LOG --log-prefix hello index 100
 tablename: mangle hook: NF_IP_POST_ROUTING
         target:  LOG level warning prefix "hello" index 100
 # tc action show action xt
 total acts 1

         action order 0: tablename: mangle  hook: NF_IP_POST_ROUTING
         target  LOG level warning prefix "hello"
         index 100 ref 1 bind 0
 # tc action replace action xt -j LOG --log-prefix world index 100
 tablename: mangle hook: NF_IP_POST_ROUTING
         target:  LOG level warning prefix "world" index 100
 RTNETLINK answers: Cannot allocate memory
 We have an error talking to the kernel
 # tc action show action xt
 total acts 1

         action order 0: tablename: mangle  hook: NF_IP_POST_ROUTING
         target  LOG level warning prefix "hello"
         index 100 ref 2 bind 0

Ensure we call tcf_idr_release(), in case 'tname' allocation failed, also
when the action is being replaced.

Fixes: 4e8ddd7f ("net: sched: don't release reference on action overwrite")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>