Regression bug: "confirmed_only" config parameter no longer respected on RPC calls

[johnzweng]

Bug:

• confirmed_only Config parameter allows to define unconfirmed utxos should be included when creating transactions or not
• this was working fine
• since version 4.4.0 this parameter no longer gets respected when creating transactions via RPC using payto or paytomany
• According to ghost43 (on IRC) open_channel and normal_swap also are affected
• The concrete commit where the behaviour changed was this: 2f6d60c in line 929 in electrum/wallet.py
• Reason: the Abstract_Wallet.get_spendable_coins(…) function gets called without explicitly specifying the confirmed_only argument here and in the method Abstract_Wallet.get_spendable_coins(…) the default value for confirmed_only is False

Expected behaviour:

• when config parameter confirmed_only is set to True and transactions are created via RPC payto/paytomany call, the method Abstract_Wallet.get_spendable_coins(…) should be called with confirmed_only: True, so that no unconfirmed coins are used in the transaction.
• Optionally: provide a commandline argument to override the config parameter confirmed_only on a per transaction base