use prepare_for_testing in gdb.python/py-frame.exp

gdb/testsuite/ChangeLog:

        * gdb.python/py-frame.exp: Simplify the initialization phase
        using prepare_for_testing.

gdb/testsuite/gdb.python/py-frame.exp

@@ -24,19 +24,10 @@ load_lib gdb-python.exp
 
 set testfile "py-frame"
 set srcfile ${testfile}.c
-set binfile ${objdir}/${subdir}/${testfile}
-if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
-    untested "Couldn't compile ${srcfile}"
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
     return -1
 }
 
-# Start with a fresh gdb.
-
-gdb_exit
-gdb_start
-gdb_reinitialize_dir $srcdir/$subdir
-gdb_load ${binfile}
-
 # Skip all tests if Python scripting is not enabled.
 if { [skip_python_tests] } { continue }