add ; to list of shell escaped chars in sub_test.py

[arezaii]

This adds the semicolon character to the list of special escaped characters in two functions we use for preparing test command strings in sub_test.py.

It was needed to accommodate HPO testing where the execopts expect to pass a ; as the delimiter between arguments for the hpo-example.chpl blog article. I found that when start_test was used the program was not seeing any arguments after the first ; in the argsString argument. Manually escaping the character did not work, but adding the ; to the list of escaped characters in these ShellEscape and ShellEscapeCommand did.

TESTING:

• paratest [Summary: #Successes = 17653 | #Failures = 0 | #Futures = 0]
• paratest w/gasnet [Summary: #Successes = 17835 | #Failures = 0 | #Futures = 0]