Describe the bug

A short description of the bug.

1:S 13 Nov 2020 06:18:06.183 # == CRITICAL == This replica is sending an error to its master: 'MULTI calls can not be nested' after processing the command 'multi'

To reproduce

1、in redismodule, register mydel command and sub callback
2、delete a key in mydel command (del keya) . and the del cmd need propagateto replica.
3、step 2 delete action will trigger step 1 sub callback. in sub callback, a propagate command is executed (del keyb).

master will generate coomand:

multi    //generate by del keya in custom module command
multi    //generate by del keyb in subscribe callback
del keyb
exec     //generate by del keyb in subscribe callback
del keya
exec     //generate by del keya in custom module command

Reason
when trigger sub callback ,a new RedisModuleContext will be generated. the "REDISMODULE_CTX_MULTI_EMITTED" in old ctx is lost.