core/utils: cleanup if condition

uwsgi.ksm_mappings_current_size cannot be 0 here.
A couple of lines above:

1219 if (uwsgi.ksm_mappings_current_size <= 0) {
1220     uwsgi_log("[uwsgi-KSM] unable to read /proc/self/maps data\n");
1221     return;
1222 }
plugins/router_hash: don't dereference a null pointer

In case this condition is true:

    if (urhc->items[i] == ';') {

but this is false:

    if (found == hashed_result)

for the latest loop iteration value would be set as NULL

This is a bit unfortunate because later we can:
- use it in arithmetics
- dereference it in uwsgi_req_append

To fix that update vallen only if value is not null.

Reported by Coverity sa CID #1100805.
core/fifo: check array index read before dereferencing uwsgi_master_fifo_manage

Reported by Coverity as CID #1100821
plugins/gevent: don't dereference null pointer

We should not pass a NULL pointer to Py_DECREF. This is possible
if wsgi_req->socket->edge_trigger is true.

Reported by Coverity as CID #970981.
Merge pull request #433 from xrmx/coverity2810-2

More Coverity fixes
little optimization in master fifo
enable switching stats source from carbon's own loop to metrics data, fixes #417
Merge pull request #435 from prymitive/carbon_use_metrics

enable switching stats source from carbon's own loop to metrics data
port the carbon metric feature to latest api
fixed #436
correctly support python2.4
add retry support to stats pusher
port carbon plugin to support retries in stats pusher, replaces old non-functional retry handling
Merge pull request #437 from prymitive/stats_pusher_retry

Restore retry handling in carbon