Fix for URLConnection.getInputStream() Crashing

[argzdev]

Proposed fix for #5584:

Issue

Crash happens if a URL connection is opened e.g. url.openStream() when FirebasePerformance has not been initialized.

Investigation

1. openStream in FirebasePerfUrlConnection intercepts all urls that opens connections.
2. openStream requires TransportManager to be initialized
3. TransportManager is only initialized after FirebasePerformance has been initialized

Solution

If TransportManager is not initialized, we should simply return the URL openStream and not intercept the connection.