display: lock: Relocate custom_holdkey_block variable

display: lock: Relocate custom_holdkey_block variable

To remove build dependency, custom_holdkey_block variable should be moved to display-lock.
And then, custom_holdkey_block getter/setter is added.
void display_lock_set_custom_holdkey_block(bool blocked);
void display_lock_get_custom_holdkey_block(bool *blocked);

custom_holdkey_block is set through the dbus method dbus_setlcdtimeout.
This variable is used for screenlock, lcdoff process.

Change-Id: If8b19fd66d388271ccc51c327302ed00196097f7
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>