hla_target: Update target state when polling

hla_target: Update target state when polling

    Polling target does not change stste information
    except if new state is TARGET_HALTED.
    Connecting to the runing target result in target->state
    not updated with retrieved value and remains "UNKNOWN"
    until 'halt' command issued.

Change-Id: I803d6c0207f7f8699e648779d1df342c9ee7315a
Signed-off-by: Sergey A. Borshch <sb-sf@users.sourceforge.net>
Reviewed-on: http://openocd.zylin.com/1680
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>