test: allow passing empty coreP2PAddrs to MasternodeInfo helpers

`or` will treat a blank string as a bad value and will go for the
default, which creates problems when we need to test for blank value
behaviors. This isn't a problem with `platform_{p2p,http}_port` since we
check against None explicitly.

Author: kwvg

test/functional/test_framework/test_framework.py

@@ -1242,7 +1242,7 @@ def register(self, node: TestNode, submit: bool, collateral_txid: Optional[str]
         args = [
             collateral_txid or self.collateral_txid,
             collateral_vout or self.collateral_vout,
-            addrs_core_p2p or [f'127.0.0.1:{self.nodePort}'],
+            [f'127.0.0.1:{self.nodePort}'] if addrs_core_p2p is None else addrs_core_p2p,
             ownerAddr or self.ownerAddr,
             pubKeyOperator or self.pubKeyOperator,
             votingAddr or self.votingAddr,
@@ -1306,7 +1306,7 @@ def register_fund(self, node: TestNode, submit: bool, collateral_address: Option
         # Common arguments shared between regular masternodes and EvoNodes
         args = [
             collateral_address or self.collateral_address,
-            addrs_core_p2p or [f'127.0.0.1:{self.nodePort}'],
+            [f'127.0.0.1:{self.nodePort}'] if addrs_core_p2p is None else addrs_core_p2p,
             ownerAddr or self.ownerAddr,
             pubKeyOperator or self.pubKeyOperator,
             votingAddr or self.votingAddr,
@@ -1450,7 +1450,7 @@ def update_service(self, node: TestNode, submit: bool, addrs_core_p2p: Union[str
         # Common arguments shared between regular masternodes and EvoNodes
         args = [
             self.proTxHash,
-            addrs_core_p2p or [f'127.0.0.1:{self.nodePort}'],
+            [f'127.0.0.1:{self.nodePort}'] if addrs_core_p2p is None else addrs_core_p2p,
             self.keyOperator,
         ]
         address_funds = fundsAddr or self.fundsAddr