pw_env_setup: Run deactivate if detected

Run deactivate.sh if found at the beginning of bootstrap. This should
allow shells to be reused for different projects.

Change-Id: I8af4de92b528a81c4afeb822699d2e016ffcb42f
Bug: 278
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/22580
Commit-Queue: Rob Mohr <mohrr@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
diff --git a/bootstrap.sh b/bootstrap.sh
index 8321bf3..246d007 100644
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -71,6 +71,7 @@
 
 . "$PW_ROOT/pw_env_setup/util.sh"
 
+pw_deactivate
 pw_eval_sourced "$_pw_sourced"
 pw_check_root "$PW_ROOT"
 _PW_ACTUAL_ENVIRONMENT_ROOT="$(pw_get_env_root)"