don't blindly reuse content providers

when a provider is already running, we would automatically
give it out to other processes that request it. for instant
apps, don't do that.

Change-Id: I159913adc599e88dac6253104776589592b251fd
Fixes: 37501319
Test: cts-tradefed run commandAndExit cts-dev -m CtsAppSecurityHostTestCases -t android.appsecurity.cts.EphemeralTest