Description: tcp: Clear sk_send_head after purging the write queue
References:
 https://source.android.com/security/bulletin/2020-03-01
 https://android.googlesource.com/kernel/common/+/3ed1460d6b17326093eb657afa89a7274e444a32%5E%21/#F0
Notes:
 jmm> For 4.9.x broken backport was added in 4.9.103
 carnil> This is actually a duplicate of CVE-2019-15239, will contact
 carnil> Android security team to get the CVE sorted out and potentially
 carnil> rejected.
Bugs:
upstream: N/A
4.19-upstream-stable: N/A 
4.9-upstream-stable:
3.16-upstream-stable:
sid: N/A
4.19-buster-security: N/A
4.9-stretch-security:
3.16-jessie-security: