cutils: str_parms: when deleting entry, need to also remove key

When removing one entry, we can't just remove it from the map since
key will not be freed. So, instead, search through the map for the key
and free it once it is found.

Change-Id: Id745c166a4acc5ea25f6d6cdbfe4f8fbc21cbbb3
Reported-by: Xin Qian <xqian@marvell.com>
Signed-off-by: Dima Zavin <dima@android.com>