wallet2::import_multisig doesn't signal about error if refresh failed

[naughtyfox]

We encountered the following bug - if refresh error happens like wallet disconnected from daemon when multisig wallets exchange with multisig key images wallet2::import_multisig function does not indicate that operation is failed. Client code cannot determine if operation has been successful. This happens because sync exception just captured and wasn't propogated to the calling code (

monero/src/wallet/wallet2.cpp

Line 10881 in fad88e1

catch (...) {}

).

This kind of error occurs especially often on mobile devices where connectivity may be not stable.

[moneromooo-monero]

+resolved