Minor tweaks to name_sendcoins.py.
Minor tweaks to name_sendcoins.py.

Some small improvements and tweaks to the name_sendcoins.py test.  Formatting
fixes and assert that the transactions are actually mined (and not e.g.
considered non-standard / not accepted to the mempool).

pataquets/namecoin-core,domob1812/namecore,namecoin/namecoin-core,pataquets/namecoin-core,domob1812/namecore,namecoin/namecoin-core,namecoin/namecore,pataquets/namecoin-core,domob1812/namecore,pataquets/namecoin-core,domob1812/namecore,pataquets/namecoin-core,namecoin/namecoin-core,domob1812/namecore,namecoin/namecore,domob1812/namecore,pataquets/namecoin-core,namecoin/namecore,namecoin/namecore,namecoin/namecoin-core,namecoin/namecoin-core,namecoin/namecoin-core,namecoin/namecore,namecoin/namecore