core: prefer strncpy over strcpy in emperor

Coverity reports a possible buffer overrun which is not possible
at the momento because the only caller of uwsgi_emperor_blacklist_add
use another fixed buffer of the same size as te one we are writing
to. Still better safe than sorry. Reported as CID #971078.
plugins/python: remove double assignment to same variable

Which coverity reports as undefined behaviour in CID #970978.
plugins/python: check return value of PyType_Ready in init_uwsgi_embedded_module

Reported by Coverity as CID #970972.
core/socket: fix a couple of memory leaks

Reported by Coverity as CID #971053, #971054.
plugins/python: fix a couple of memory leaks

Reported by Coverity as CID #971065, #971066.
plugins/python: fix tracebaker resource leaks on import error

Reported by Coverity as CID #971061, #971062, #971063.
plugin/python: fix some leaks on error paths in symimporter

Reported by Coverity as CID #971059, #971060.
Merge pull request #136 from xrmx/coverity4

More issues reported by Coverity