Don't use is_available() for HW wallets

is_available() is only used from generic code for non-hardware
wallets.  Having a local function of the same name is confusing.

plugins/ledger/ledger.py

@@ -421,31 +421,22 @@ class LedgerPlugin(BasePlugin):
 
     def __init__(self, parent, config, name):
         BasePlugin.__init__(self, parent, config, name)
-        self._is_available = self._init()
         self.wallet = None
         self.handler = None
 
     def constructor(self, s):
         return BTChipWallet(s)
 
-    def _init(self):
-        return BTCHIP
+    def set_enabled(self, enabled):
+        self.wallet.storage.put('use_' + self.name, enabled)
 
-    def is_available(self):
-        if not self._is_available:
+    def is_enabled(self):
+        if not BTCHIP:
             return False
         if not self.wallet:
             return False
         if self.wallet.storage.get('wallet_type') != 'btchip':
             return False
-        return True
-
-    def set_enabled(self, enabled):
-        self.wallet.storage.put('use_' + self.name, enabled)
-
-    def is_enabled(self):
-        if not self.is_available():
-            return False
         if self.wallet.has_seed():
             return False
         return True

plugins/trezor/plugin.py

@@ -165,19 +165,16 @@ class TrezorCompatiblePlugin(BasePlugin):
         self.print_error(message)
         raise Exception(message)
 
-    def is_available(self):
-        if not self.libraries_available:
-            return False
-        if not self.wallet:
-            return False
-        wallet_type = self.wallet.storage.get('wallet_type')
-        return wallet_type == self.wallet_class.wallet_type
-
     def set_enabled(self, enabled):
         self.wallet.storage.put('use_' + self.name, enabled)
 
     def is_enabled(self):
-        if not self.is_available():
+        if not self.libraries_available:
+            return False
+        if not self.wallet:
+            return False
+        wallet_type = self.wallet_class.wallet_type
+        if self.wallet.storage.get('wallet_type') != wallet_type:
             return False
         if self.wallet.has_seed():
             return False