AWS executor: update http requests
AWS executor: update http requests

This commit includes the following:
- Adding a timeout of 10 seconds for http requests
- Pass data using the 'params' paramter in 'requests.get()'
- Use UTF-8 encoding for the urls
- Renaming of local variables such that they follow a consistent naming
scheme

dbeyer/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,dbeyer/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,dbeyer/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,dbeyer/benchexec,ultimate-pa/benchexec