lib: util: fixup possible bad pointer return in get_string_arg
lib: util: fixup possible bad pointer return in get_string_arg

get_string_arg might return a pointer to argv[argc] which could point to
anything. Fix by looping only to argc - 1.

cp16net/virgo-base,AlphaStaxLLC/rackspace-monitoring-agent,kaustavha/rackspace-monitoring-agent,christopherjwang/rackspace-monitoring-agent,cp16net/virgo-base,virgo-agent-toolkit/rackspace-monitoring-agent,christopherjwang/rackspace-monitoring-agent,kaustavha/rackspace-monitoring-agent,cp16net/virgo-base,virgo-agent-toolkit/rackspace-monitoring-agent,cp16net/virgo-base,cp16net/virgo-base,AlphaStaxLLC/rackspace-monitoring-agent