PAN: Delete disconnected PAN device from map

Usecase:
1) Pair and connect DUT (PANU) to remote device (RD1) in NAP role.
2) Disconnect DUT and remote device (RD1).
3) Disable BT on remote device (RD1).
4) Enable BT Tethering on DUT and enable Wifi connection or SIM data to act as
   backhaul so that DUT acts in NAP Role
5) Pair and connect DUT with remote device (RD2) in PANU role and browse internet.
6) Disconnect DUT and RD2.
7) Intiate connection from DUT to RD1 (It should fail after page connection timeout of 5 sec).
8) Connect from RD2 to DUT and try to browse internet.
9) Disconnect DUT connection from RD2.
10) Connect from RD2 to DUT.

Failure:
Browsing is not working with remote (RD2) PANU Device.

Fix:
Remove pan device from hashmap with out considering previous state of remote device.

Test: Remote device can browse internet without issues as per usecase above.

Fixes: 70559095
Change-Id: I28c8014a6ca0c22b7d15000b23fe8b12feb75026