filestore: fix crash if keyword setup fails

SigMatch would be added to list, then the alproto check failed, leading
to freeing of sm. But as it was still in the list, the list now contained
a dangling pointer.
smtp: don't create a new tx for rset/quit

A tx is considered complete after the data command completed. However,
this would lead to RSET and QUIT commands setting up a new tx.

This patch simply adds a check that refuses to setup a new tx when these
commands are encountered after the data portion is complete.
Fix Coverity issue in SMTP output

** CID 1250327:  Uninitialized pointer read  (UNINIT)
/src/output-json-email-common.c: 117 in JsonEmailLogJson()
/src/output-json-email-common.c: 139 in JsonEmailLogJson()