Revert "Always disconnect agents immediately."

This reverts commit 4bc9fa6b8cefca88f1065e95df06532979c202ee.

Reason for revert: b/288450518

Some iterations over mNetworkAgentInfos result in networks being
disconnected, which removes them from mNetworkAgentInfos during
iteration. This crashes with NPE or OOB exceptions.

Bug: 286649301
Bug: 288149251
Bug: 288450518
(cherry picked from https://android-review.googlesource.com/q/commit:3160bc0825490353d79c6586e21a7fc5893c678d)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:2a2b911a31e9996382eef9f61c7600dc30dd29ff)
Merged-In: I6e0b5b614d9e88267db77cb807ae4bf09f88c0f6
Change-Id: I6e0b5b614d9e88267db77cb807ae4bf09f88c0f6
3 files changed