Fix file descriptor leak when executing CA helpers
cm_cadata_start_generic() creates a pipe. One half is passed
to fetch(), the function that does all helper calls,
via the cm_cadata_state variable ret. The other half is the
reader and is used to detect execution errors. There is a pair
of write/read on this descriptor which on error would be the
errno.
This second half wasn't being closed after reading to test for
errors.
https://bugzilla.redhat.com/show_bug.cgi?id=1992439
Signed-off-by: Rob Crittenden <rcritten@redhat.com>