MINOR: ssl: refine the error testing for fc_err and fc_err_str

MINOR: ssl: refine the error testing for fc_err and fc_err_str

In issue #1645, coverity suspects some dead code due to a pair of
remaining tests on "if (!ctx)". While all other functions test the
context earlier, these ones used to only test the connection and the
transport. It's still not very clear to me if there are certain error
cases that can lead to no SSL being initially set while the rest is
ready, and the SSL arriving later, but better preserve this original
construct by testing first the connection and only later the context.