Move traceframe checking out of traceframe generation

This patch moves traceframe checking code out of traceframe generation,
so that we can generation traceframe once, and do the checking in multiple
times (with target remote, tfile and ctf respectively).  This is a
pure refactor, not functional changes in unavailable.exp.

gdb/testsuite:

2014-05-05  Yao Qi  <yao@codesourcery.com>

	* gdb.trace/unavailable.exp (gdb_collect_args_test): Move some
	code to ...
	(gdb_collect_args_test_1): ... it.  New proc.
	(gdb_collect_locals_test): Move some code to ...
	(gdb_collect_locals_test_1): ... it.  New proc.
	(gdb_unavailable_registers_test): Move some code to ...
	(gdb_unavailable_registers_test_1): ... it.  New proc.
	(gdb_unavailable_floats): Move some code to ...
	(gdb_unavailable_floats_1): ... it.  New proc.