Prevent Bitcoin observer starting watcher routines if Bitcoin is not enabled

[lumtis]

Describe the Issue
When testing in localnet without Bitcoin node enable, extensive logs are shown as the observer starts the watcher routines:

zetaclient0  | �[90m2024-08-27T12:22:56Z�[0m �[1m�[31mERR�[0m�[0m error fetching btc utxos �[36merror=�[0m�[31m"-18: No wallet is loaded. Load a wallet using loadwallet or create a new one with createwallet. (Note: A default wallet is no longer automatically created)"�[0m �[36mchain=�[0mbtc_regtest �[36mmodule=�[0mWatchUTXOS
zetaclient0  | �[90m2024-08-27T12:22:57Z�[0m �[1m�[31mERR�[0m�[0m WatchInTx error observing in tx �[36merror=�[0m�[31m"observeInTxBTC: skipping observer, current block number 0 is too low"�[0m �[36mchain=�[0mbtc_regtest �[36mmodule=�[0mWatchInTx
zetaclient0  | �[90m2024-08-27T12:22:57Z�[0m �[1m�[31mERR�[0m�[0m error fetching btc utxos �[36merror=�[0m�[31m"-18: No wallet is loaded. Load a wallet using loadwallet or create a new one with createwallet. (Note: A default wallet is no longer automatically created)"�[0m �[36mchain=�[0mbtc_regtest �[36mmodule=�[0mWatchUTXOS
zetaclient0  | �[90m2024-08-27T12:22:58Z�[0m �[1m�[31mERR�[0m�[0m WatchInTx error observing in tx �[36merror=�[0m�[31m"observeInTxBTC: skipping observer, current block number 0 is too low"�[0m �[36mchain=�[0mbtc_regtest �[36mmodule=�[0mWatchInTx
zetaclient0  | �[90m2024-08-27T12:22:58Z�[0m �[1m�[31mERR�[0m�[0m error fetching btc utxos �[36merror=�[0m�[31m"-18: No wallet is loaded. Load a wallet using loadwallet or create a new one with createwallet. (Note: A default wallet is no longer automatically created)"�[0m �[36mchain=�[0mbtc_regtest �[36mmodule=�[0mWatchUTXOS
zetaclient0  | �[90m2024-08-27T12:22:59Z�[0m �[1m�[31mERR�[0m�[0m WatchInTx error observing in tx �[36merror=�[0m�[31m"observeInTxBTC: skipping observer, current block number 0 is too low"�[0m �[36mchain=�[0mbtc_regtest �[36mmodule=�[0mWatchInTx
zetaclient0  | �[90m2024-08-27T12:22:59Z�[0m �[32mINF�[0m observeInTX: lasstScanned heights for chain 1337 ZetaSent 58 ERC20Deposited 58 TssRecvd 58 �[36mchain=�[0mgoerli_localnet �[36mmodule=�[0mWatchInTx
zetaclient0  | �[90m2024-08-27T12:22:59Z�[0m �[1m�[31mERR�[0m�[0m error fetching btc utxos �[36merror=�[0m�[31m"-18: No wallet is loaded. Load a wallet using loadwallet or create a new one with createwallet. (Note: A default wallet is no longer automatically created)"�[0m �[36mchain=�[0mbtc_regtest �[36mmodule=�[0mWatchUTXOS
zetaclient0  | �[90m2024-08-27T12:23:00Z�[0m �[1m�[31mERR�[0m�[0m WatchInTx error observing in tx �[36merror=�[0m�[31m"observeInTxBTC: skipping observer, current block number 0 is too low"�[0m �[36mchain=�[0mbtc_regtest �[36mmodule=�[0mWatchInTx
......

#2763 mitigates some of the extensive logging but we should prevent completely the routines from starting if the node is not enabled