fix some missing awaits in functional tests

[spalger]

I've noticed a couple UnhandledPromiseRejections, and they seem to be inside of retry.try() calls, so looked around and found these beauties :)

(node:27086) UnhandledPromiseRejectionWarning: Error: retry.try timeout: Error: expected false to equal true
    at Assertion.assert (/dev/shm/workspace/kibana/packages/kbn-expect/expect.js:100:11)
    at Assertion.be.Assertion.equal (/dev/shm/workspace/kibana/packages/kbn-expect/expect.js:227:8)
    at Assertion.be (/dev/shm/workspace/kibana/packages/kbn-expect/expect.js:69:22)
    at retry.try (/dev/shm/workspace/kibana/test/functional/apps/context/_filters.js:70:14)
    at process._tickCallback (internal/process/next_tick.js:68:7)
    at onFailure (/dev/shm/workspace/kibana/test/common/services/retry/retry_for_success.ts:28:9)
    at retryForSuccess (/dev/shm/workspace/kibana/test/common/services/retry/retry_for_success.ts:68:13)
(node:27086) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 28)

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 8b114ae

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[kibanamachine]

Looks like this PR has a backport PR but it still hasn't been merged. Please merge it ASAP to keep the branches relatively in sync.

[kibanamachine]

Looks like this PR has a backport PR but it still hasn't been merged. Please merge it ASAP to keep the branches relatively in sync.

[kibanamachine]

Looks like this PR has a backport PR but it still hasn't been merged. Please merge it ASAP to keep the branches relatively in sync.

[spalger]

7.x/7.7: d007b0a