Make hrSWRunPath use argv[0], instead of p_comm. hrSWRunName is supposed

Make hrSWRunPath use argv[0], instead of p_comm. hrSWRunName is supposed
to be a descriptive name, where hrSWRunPath should give the full path to
the binary. While argv[0] can contain any of a simple binary name, the
full path, or a custom name given by the application itself, it gives us
the option to retrieve both pieces of information. This is also the
same distinction made by netsnmp.

This also keeps the default command column from top(1) and snmptop in
sync, and now allows for identical output in the column between `top -C`
and `snmptop -Cpa`

OK tb@