BT: Add CAP_NET_ADMIN for Bluetooth Process

Precondition:
1. A reference phone has internet connection and with BT tethering enabled.
2. DUT is in PANU role & Remote is NAP role
Or
1. DUT has internet connection and with BT tethering enabled.
2. DUT is in NAP role & Remote is PANU role.

Use case:
1. Connect DUT(PANU) to reference phone(NAP).
2. Internet browse is not working on DUT & Connection is dropped from DUT.
Or
1. Connect remote(PANU) to Remote device(NAP).
2. Internet browse is not working on remote & Connection is dropped fro DUT.

RCA:
https://android-review.googlesource.com/c/kernel/common/+/936980 will cause this issue. If it's cherrypicked in codebase.
TUNSETIFF ioctl call is being failed due to Operation not permitted error, Hence bt-pan interface is not being up.&
connection is dropped.
06-04 23:18:06.856  6173  6699 D bt_btif : ioctl error:-1, errno:Operation not permitted

TEST:
1. Connect DUT(PANU) to reference phone(NAP).
2. Internet browse is  working on DUT
Or
1. Connect remote(PANU) to Remote device(NAP).
2. Internet browse is working on remote.

Fix:
BT Process need CAP_NET_ADAMIN capability to make
ioctl call to TUN driver from BT PAN module. Hence
adding CAP_NET_ADMIN capablity for BT

Bug: 133735703
Bug: 135707477
Change-Id: Ie461bfee7a8221404ed6b9852bd5d36758d094df
Merged-In: Ie461bfee7a8221404ed6b9852bd5d36758d094df
(cherrypicked from 99cec9d9)