[RHEL/6] Use full path for 'chkconfig' & 'service' commands in RHEL-6 service related remediation scripts

As noted in further detail in issue:
  [1] https://github.com/OpenSCAP/scap-security-guide/issues/313

oscap when running remediation script calls execve() with restricted environment. As a result the corresponding $PATH variable content is restricted to executables just from
   ```/usr/local/bin, /usr/bin, /bin``` directories.

Since ```chkconfig``` and ```service``` command live in ```/sbin``` directory on RHEL-6, attempt to perform:
* service * enabled
* service * disabled
script will result with error, as can be seen e.g. at:

&nbsp; &nbsp; [2]  https://jlieskov.fedorapeople.org/oscap_usgcb_remediation_report.html

(see those 11 rules returning error)

Therefore modify RHEL-6 remediation scripts for ```service * enabled``` / ```service * disabled``` they to use full path when calling ```chkconfig``` and / or ```service``` commands respectively.