adb-remount-test: parameterize fastboot_wait & adb_wait, increase timeout

Increase adb_wait time to 3 minutes since blueline device takes
maximum 2:38 (ten samples) to perform a ramdump should an
inopportune kernel panic occur.

Test: adb-remount-test.sh
Bug: 132070014
Change-Id: Icfbb799f9420035a755090c9fc5fc2ee05dd68d3