Initialize PipTaskOrganizer in ShellInit

Follows the same initialize process in other classes. This makes sure
the DisableFlag annotation in pip1 unit tests work properly, since we
can forcefully call the onInit function, regardless the flag value.

Further, change the pattern in pip1 unit tests to not rely on the
ShellInit, instead, calling the onInit directly to bypass the flag check

Flag: EXEMPT testfix
Bug: 409622499
Test: atest WMShellUnitTests
Change-Id: If5ff059235b4af744dd71d21b7e8f775ce0828a0