message: test: check that CSV/CLTV are active in rpc_signrawtransaction
  Without this check, the tests would also pass if the CSV and
  CLTV activation heights are not reached yet (e.g. if the .generate()
  calls before are removed), as the operations OP_CSV and OP_CLTV
  simply behave as NOPs.
  Also fixes a comment in the sub-test `test_signing_with_cltv()`.
diff: @@ -271,6 +271,7 @@ class SignRawTransactionsTest(BitcoinTestFramework):
  # Make sure CSV is active
  self.nodes[0].generate(500)
  + assert self.nodes[0].getblockchaininfo()['softforks']['csv']['active']
  # Create a P2WSH script with CSV
  script = CScript([1, OP_CHECKSEQUENCEVERIFY, OP_DROP])
  @@ -304,8 +305,9 @@ class SignRawTransactionsTest(BitcoinTestFramework):
  self.nodes[0].walletpassphrase("password", 9999)
  getcontext().prec = 8
  - # Make sure CSV is active
  + # Make sure CLTV is active
  self.nodes[0].generate(1500)
  + assert self.nodes[0].getblockchaininfo()['softforks']['bip65']['active']
  # Create a P2WSH script with CLTV
  script = CScript([1000, OP_CHECKLOCKTIMEVERIFY, OP_DROP])
  