Check for TEST_VISTA_FRESH variables during configure

There is currently no check that the variables that appear after
selecting the TEST_VISTA_FRESH option have been defined prior to use.

Add a check for the variables by adding the variable to a list,
looping through the list to visit each, and check that it is defined.
If it is not, display an error to say that the variable needs to be defined
before configuring.

OSEHRA-Issue: http://issues.osehra.org/browse/OAT-53
Change-Id: I865959adb805dc566a4ce492cbe919114fd12c5b
VistATestClient: handle non-default initial cache prompt

Change waitForPrompt to expect('>') instead.

OSEHRA-Id: http://issues.osehra.org/browse/OAT-54

Change-Id: I5161b7274f3797568f711b23c68b5f8428fbbaa5
Merge "VistATestClient: handle non-default initial cache prompt"