jobcomp/elasticsearch fixes

There were a few minor problems and enhancements to the original code
* There were some missing header files includes
* derived_exitcode needs to be printed as %lu rather than %hu.
* the fsize variable was set and never read
* I added some "static" definitions on functions
* Some compilers report warnings for variables definitions NOT at the start of a block (I needed to use xmalloc for the pop_marks variable)
* Some compilers report warnings for the xrealloc return value not used
* In the log functions you are testing for empty strings, so testing if the first character is '\0' is faster than using strlen()
* The xstrfmtcat is faster than using a temporary value and copying data
* slurmdb_association_rec_t was changed to slurmdb_assoc_rec_t