lowmemorykiller: Account for extra_free_kbytes in calcuations

Account for extra_free_kbytes in calcuations

CRs-fixed: (CR)
Signed-off-by: Jeff Vanhoof <qjv001@motorola.com>
Change-Id: I2c44a1775d43fad40cf49d6303b7552c2c089b6e
Reviewed-on: https://gerrit.mot.com/1076213


SME-Granted: SME Approvals Granted
SLTApproved: Slta Waiver
Tested-by: Jira Key
Reviewed-by: Coverity Analysis <coverity@motorola.com>
Reviewed-by: Igor Kovalenko <igork@motorola.com>
Submit-Approved: Jira Key