Add timeout to run_host() in openssl_heartbleed

Added timeout to run_host() to prevent the scanner from hanging on some systems. Default timeout is 10 seconds.

Console output:

msf auxiliary(openssl_heartbleed) > run -j
[*] Auxiliary module running as background job
[-] 192.168.1.3:443 - Timed out after 10 seconds
[+] 192.168.1.4:443 - Heartbeat response with leak
[-] 192.168.1.5:443 - Timed out after 10 seconds