[PT14] No-op refactoring of sendProxyBroadcast

If mGlobalProxy is non-null, then getDefaultProxy returns mGlobalProxy
so the first change is a no-op.
If mGlobalProxy is null and mDefaultProxyEnabled is true, then
getDefaultProxy returns mDefaultProxy, which has just been set to
proxyInfo, so the second change is a no-op.
If mGlobalProxy is null and mDefaultProxyEnabled is true, then
getDefaultProxy returns mDefaultProxy ; if mGlobalProxy is null and
mDefaultProxyEnabled is false, then getDefaultProxy returns null,
therefore the third change is a no-op.

Test: runtest
Change-Id: I7c21062302bf54f4fc917c82e0175975051a55ec