ktest: Add support for meta characters in GRUB_MENU

ktest: Add support for meta characters in GRUB_MENU

ktest fails if meta characters are in GRUB_MENU, for example
GRUB_MENU = 'Fedora (test)'

The failure happens because the meta characters are not escaped,
so the menu doesn't match in any entries in GRUB_FILE.

Use quotemeta() to escape the meta characters.

Link: http://lkml.kernel.org/r/20190417235823.18176-1-msys.mizuma@gmail.com
Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>