Current behavior in megatest is to look in runconfig for a TESTPATT setting if a testpatt is not specified on the command line.

This request is to enhance the behavior to add a -testpattvar parameter that takes a runconfig setting name to use for the default testpatt.

The testpattvar should be an optional argument that defaults to TESTPATT.

Sample usage: megatest -run -runname foo -target foo/bar -testpattvar FOOPATT.