libprocessgroup: Prevent SetProcessProfiles from using cached fd

Because we cache file descriptors associated with cgroup "tasks" file it
should not be used with SetProcessProfiles API which operates on entire
processes rather than tasks. Change SetProcessProfiles API to prevent
cache fd usage, modify ExecuteForProcess to not attempt to use cached
fd. Also fix unconditional calls to EnableResourceCaching from
ExecuteForTask which should be called only when SetTaskProfiles is used
with use_fd_cache set to true.

Bug: 149524788
Change-Id: I880efaf8217a4dd7ccfbb4fb167b2295cefc057a
Signed-off-by: Suren Baghdasaryan <surenb@google.com>